Rules In DISA STIG for Red Hat Enterprise Linux 6

V-ID | CCI | CAT | Title | Description | Check Procedures | Fixtext

RHEL-06-000001

CCI-000366

low

The system must use a separate file system for /tmp.

The `/tmp` partition is used as temporary storage by many programs. Placing `/tmp` in its own partition enables the setting of more restrictive mount options, which can help protect programs which use it.

If , this is a finding.

The `/tmp` directory is a world-writable directory used for temporary file storage. Ensure it has its own partition or logical volume at installation time, or migrate it using LVM.

RHEL-06-000002

CCI-000366

low

The system must use a separate file system for /var.

Ensuring that `/var` is mounted on its own partition enables the setting of more restrictive mount options. This helps protect system services such as daemons or other programs which use it. It is not uncommon for the `/var` directory to contain world-writable directories installed by other software packages.

If , this is a finding.

The `/var` directory is used by daemons and other system services to store frequently-changing data. Ensure that `/var` has its own partition or logical volume at installation time, or migrate it using LVM.

RHEL-06-000003 | CCI-000366 | low | The system must use a separate file system for /var/log. | Placing `/var/log` in its own partition enables better separation between log files and other files in `/var/`. | If , this is a finding. | System logs are stored in the `/var/log` directory. Ensure that it has its own partition or logical volume at installation time, or migrate it using LVM.

RHEL-06-000004

CCI-000137

low

The system must use a separate file system for the system audit data path.

Placing `/var/log/audit` in its own partition enables better separation between audit files and other files, and helps ensure that auditing cannot be halted due to the partition running out of space.

If , this is a finding.

Audit logs are stored in the `/var/log/audit` directory. Ensure that it has its own partition or logical volume at installation time, or migrate it later using LVM. Make absolutely certain that it is large enough to store all audit logs that will be created by the auditing daemon.

RHEL-06-000005

CCI-000138

medium

The audit system must alert designated staff members when the audit storage volume approaches capacity.

Notifying administrators of an impending disk space problem may allow them to take corrective action prior to any disruption.

If , this is a finding.

The `auditd` service can be configured to take an action when disk space starts to run low. Edit the file `/etc/audit/auditd.conf`. Modify the following line, substituting ACTION appropriately:

    space_left_action = ACTION

Possible values for ACTION are described in the `auditd.conf` man page. These include:

- `ignore`
- `syslog`
- `email`
- `exec`
- `suspend`
- `single`
- `halt`

Set this to `email` (instead of the default, which is `suspend`) as it is more likely to get prompt attention. Acceptable values also include `suspend`, `single`, and `halt`.

RHEL-06-000007

CCI-000366

low

The system must use a separate file system for user home directories.

Ensuring that `/home` is mounted on its own partition enables the setting of more restrictive mount options, and also helps ensure that users cannot trivially fill partitions used for log or audit data storage.

If , this is a finding.

If user home directories will be stored locally, create a separate partition for `/home` at installation time (or migrate it later using LVM). If `/home` will be mounted from another system such as an NFS server, then creating a separate partition is not necessary at installation time, and the mountpoint can instead be configured later.

RHEL-06-000008

CCI-000352

high

Vendor-provided cryptographic certificates must be installed to verify the integrity of system software.

The Red Hat GPG key is necessary to cryptographically verify packages are from Red Hat.

If , this is a finding.

To ensure the system can cryptographically verify base software packages come from Red Hat (and to connect to the Red Hat Network to receive them), the Red Hat GPG key must properly be installed. To install the Red Hat GPG key, run:

    $ sudo subscription-manager register

If the system is not connected to the Internet or an RHN Satellite, then install the Red Hat GPG key from trusted media such as the Red Hat installation CD-ROM or DVD. Assuming the disc is mounted in `/media/cdrom`, use the following command as the root user to import it into the keyring:

    $ sudo rpm --import /media/cdrom/RPM-GPG-KEY

RHEL-06-000009

CCI-000382

low

The Red Hat Network Service (rhnsd) service must not be running, unless using RHN or an RHN Satellite.

Although systems management and patching is extremely important to system security, management by a system outside the enterprise enclave is not desirable for some environments. However, if the system is being managed by RHN or RHN Satellite Server the `rhnsd` daemon can remain on.

If , this is a finding.

The Red Hat Network service automatically queries Red Hat Network servers to determine whether there are any actions that should be executed, such as package updates. This only occurs if the system was registered to an RHN server or satellite and managed as such. The `rhnsd` service can be disabled with the following command:

    $ sudo chkconfig rhnsd off

RHEL-06-000011

CCI-001233

medium

System security patches and updates must be installed and up-to-date.

Installing software updates is a fundamental mitigation against the exploitation of publicly-known vulnerabilities.

If , this is a finding.

If the system is joined to the Red Hat Network, a Red Hat Satellite Server, or a yum server, run the following command to install updates:

    $ sudo yum update

If the system is not configured to use one of these sources, updates (in the form of RPM packages) can be manually downloaded from the Red Hat Network and installed using `rpm`.

RHEL-06-000013

CCI-000663

medium

The system package management tool must cryptographically verify the authenticity of system software packages during installation.

Ensuring the validity of packages' cryptographic signatures prior to installation ensures the authenticity of the software and protects against malicious tampering.

If , this is a finding.

The `gpgcheck` option controls whether RPM packages' signatures are always checked prior to installation. To configure yum to check package signatures before installing them, ensure the following line appears in `/etc/yum.conf` in the `[main]` section:

    gpgcheck=1

RHEL-06-000015

CCI-000663

low

The system package management tool must cryptographically verify the authenticity of all software packages during installation.

Ensuring all packages' cryptographic signatures are valid prior to installation ensures the authenticity of the software and protects against malicious tampering.

If , this is a finding.

To ensure signature checking is not disabled for any repos, remove any lines from files in `/etc/yum.repos.d` of the form:

    gpgcheck=0

RHEL-06-000016

CCI-001069

medium

A file integrity tool must be installed.

The AIDE package must be installed if it is to be available for integrity checking.

If , this is a finding.

Install the AIDE package with the command:

    $ sudo yum install aide

RHEL-06-000017

CCI-000366

medium

The system must use a Linux Security Module at boot time.

Disabling a major host protection feature, such as SELinux, at boot time prevents it from confining system services at boot time. Further, it increases the chances that it will remain off during system operation.

If , this is a finding.

SELinux can be disabled at boot time by an argument in `/etc/grub.conf`. Remove any instances of `selinux=0` from the kernel arguments in that file to prevent SELinux from being disabled at boot.

RHEL-06-000018

CCI-000366

medium

A file integrity baseline must be created.

For AIDE to be effective, an initial database of "known-good" information about files must be captured and it should be able to be verified against the installed files.

If , this is a finding.

Run the following command to generate a new database:

    $ sudo /usr/sbin/aide --init

By default, the database will be written to the file `/var/lib/aide/aide.db.new.gz`. Storing the database, the configuration file `/etc/aide.conf`, and the binary `/usr/sbin/aide` (or hashes of these files), in a secure location (such as on read-only media) provides additional assurance about their integrity. The newly-generated database can be installed as follows:

    $ sudo cp /var/lib/aide/aide.db.new.gz /var/lib/aide/aide.db.gz

To initiate a manual check, run the following command:

    $ sudo /usr/sbin/aide --check

If this check produces any unexpected output, investigate.

RHEL-06-000019

CCI-001436

high

There must be no .rhosts or hosts.equiv files on the system.

Trust files are convenient, but when used in conjunction with the R-services, they can allow unauthenticated access to a system.

If , this is a finding.

The files `/etc/hosts.equiv` and `~/.rhosts` (in each user's home directory) list remote hosts and users that are trusted by the local system when using the rshd daemon. To remove these files, run the following command to delete them from any location:

    $ sudo rm /etc/hosts.equiv

    $ rm ~/.rhosts

RHEL-06-000020

CCI-000366

medium

The system must use a Linux Security Module configured to enforce limits on system services.

Setting the SELinux state to enforcing ensures SELinux is able to confine potentially compromised processes to the security policy, which is designed to prevent them from causing damage to the system or further elevating their privileges.

If , this is a finding.

The SELinux state should be set to `` at system boot time. In the file `/etc/selinux/config`, add or correct the following line to configure the system to boot into enforcing mode:

    SELINUX=

RHEL-06-000023

CCI-000366

low

The system must use a Linux Security Module configured to limit the privileges of system services.

Setting the SELinux policy to `targeted` or a more specialized policy ensures the system will confine processes that are likely to be targeted for exploitation, such as network or system services. Note: During the development or debugging of SELinux modules, it is common to temporarily place non-production systems in `permissive` mode. In such temporary cases, SELinux policies should be developed, and once work is completed, the system should be reconfigured to ``.

If , this is a finding.

The SELinux `targeted` policy is appropriate for general-purpose desktops and servers, as well as systems in many other roles. To configure the system to use this policy, add or correct the following line in `/etc/selinux/config`:

    SELINUXTYPE=

Other policies, such as `mls`, provide additional security labeling and greater confinement but are not compatible with many general-purpose use cases.

RHEL-06-000025

CCI-000366

low

All device files must be monitored by the system Linux Security Module.

If a device file carries the SELinux type `device_t`, then SELinux cannot properly restrict access to the device file.

If , this is a finding.

Device files, which are used for communication with important system resources, should be labeled with proper SELinux types. If any device files carry the SELinux type `device_t`, report the bug so that policy can be corrected. Supply information about what the device is and what programs use it.

RHEL-06-000027

CCI-000770

medium

The system must prevent the root account from logging in from virtual consoles.

Preventing direct root login to virtual console devices helps ensure accountability for actions taken on the system using the root account.

If , this is a finding.

To restrict root logins through the (deprecated) virtual console devices, ensure lines of this form do not appear in `/etc/securetty`:

    vc/1
    vc/2
    vc/3
    vc/4

RHEL-06-000028

CCI-000770

low

The system must prevent the root account from logging in from serial consoles.

Preventing direct root login to serial port interfaces helps ensure accountability for actions taken on the systems using the root account.

If , this is a finding.

To restrict root logins on serial ports, ensure lines of this form do not appear in `/etc/securetty`:

    ttyS0
    ttyS1

RHEL-06-000030

CCI-000366

high

The system must not have accounts configured with blank or null passwords.

If an account has an empty password, anyone could log in and run commands with the privileges of that account. Accounts with empty passwords should never be used in operational environments.

If , this is a finding.

If an account is configured for password authentication but does not have an assigned password, it may be possible to log onto the account without authentication. Remove any instances of the `nullok` option in `/etc/pam.d/system-auth` to prevent logins with empty passwords.

RHEL-06-000031

CCI-000366

medium

The /etc/passwd file must not contain password hashes.

The hashes for all user account passwords should be stored in the file `/etc/shadow` and never in `/etc/passwd`, which is readable by all users.

If , this is a finding.

If any password hashes are stored in `/etc/passwd` (in the second field, instead of an `x`), the cause of this misconfiguration should be investigated. The account should have its password reset and the hash should be properly stored, or the account should be deleted entirely.

RHEL-06-000032

CCI-000366

medium

The root account must be the only account having a UID of 0.

An account has root authority if it has a UID of 0. Multiple accounts with a UID of 0 afford more opportunity for potential intruders to guess a password for a privileged account. Proper configuration of sudo is recommended to afford multiple system administrators access to root privileges in an accountable manner.

If , this is a finding.

If any account other than root has a UID of 0, this misconfiguration should be investigated and the accounts other than root should be removed or have their UID changed.

RHEL-06-000033

CCI-000366

medium

The /etc/shadow file must be owned by root.

The `/etc/shadow` file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.

If , this is a finding.

To properly set the owner of `/etc/shadow`, run the command:

    $ sudo chown root /etc/shadow

RHEL-06-000034

CCI-000366

medium

The /etc/shadow file must be group-owned by root.

The `/etc/shadow` file stores password hashes. Protection of this file is critical for system security.

If , this is a finding.

To properly set the group owner of `/etc/shadow`, run the command:

    $ sudo chgrp root /etc/shadow

RHEL-06-000035

CCI-000366

medium

The /etc/shadow file must have mode 0000.

The `/etc/shadow` file contains the list of local system accounts and stores password hashes. Protection of this file is critical for system security. Failure to give ownership of this file to root provides the designated owner with access to sensitive information which could weaken the system security posture.

If , this is a finding.

To properly set the permissions of `/etc/shadow`, run the command:

    $ sudo chmod 0000 /etc/shadow

RHEL-06-000036

CCI-000366

medium

The /etc/gshadow file must be owned by root.

The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.

If , this is a finding.

To properly set the owner of `/etc/gshadow`, run the command:

    $ sudo chown root /etc/gshadow

RHEL-06-000037

CCI-000366

medium

The /etc/gshadow file must be group-owned by root.

The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.

If , this is a finding.

To properly set the group owner of `/etc/gshadow`, run the command:

    $ sudo chgrp root /etc/gshadow

RHEL-06-000038

CCI-000366

medium

The /etc/gshadow file must have mode 0000.

The `/etc/gshadow` file contains group password hashes. Protection of this file is critical for system security.

If , this is a finding.

To properly set the permissions of `/etc/gshadow`, run the command:

    $ sudo chmod 0000 /etc/gshadow

RHEL-06-000039

CCI-000366

medium

The /etc/passwd file must be owned by root.

The `/etc/passwd` file contains information about the users that are configured on the system. Protection of this file is critical for system security.

If , this is a finding.

To properly set the owner of `/etc/passwd`, run the command:

    $ sudo chown root /etc/passwd

RHEL-06-000040

CCI-000366

medium

The /etc/passwd file must be group-owned by root.

The `/etc/passwd` file contains information about the users that are configured on the system. Protection of this file is critical for system security.

If , this is a finding.

To properly set the group owner of `/etc/passwd`, run the command:

    $ sudo chgrp root /etc/passwd

RHEL-06-000041

CCI-000366

medium

The /etc/passwd file must have mode 0644 or less permissive.

If the `/etc/passwd` file is writable by a group-owner or the world the risk of its compromise is increased. The file contains the list of accounts on the system and associated information, and protection of this file is critical for system security.

If , this is a finding.

To properly set the permissions of `/etc/passwd`, run the command:

    $ sudo chmod 0644 /etc/passwd

RHEL-06-000042

CCI-000366

medium

The /etc/group file must be owned by root.

The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

If , this is a finding.

To properly set the owner of `/etc/group`, run the command:

    $ sudo chown root /etc/group

RHEL-06-000043

CCI-000366

medium

The /etc/group file must be group-owned by root.

The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

If , this is a finding.

To properly set the group owner of `/etc/group`, run the command:

    $ sudo chgrp root /etc/group

RHEL-06-000044

CCI-000366

medium

The /etc/group file must have mode 0644 or less permissive.

The `/etc/group` file contains information regarding groups that are configured on the system. Protection of this file is important for system security.

If , this is a finding.

To properly set the permissions of `/etc/group`, run the command:

    $ sudo chmod 644 /etc/group

RHEL-06-000045

CCI-001499

medium

Library files must have mode 0755 or less permissive.

Files from shared library directories are loaded into the address space of processes (including privileged ones) or of the kernel itself at runtime. Restrictive permissions are necessary to protect the integrity of the system.

If , this is a finding.

System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default:

    /lib
    /lib64
    /usr/lib
    /usr/lib64

Kernel modules, which can be added to the kernel during runtime, are stored in `/lib/modules`. All files in these directories should not be group-writable or world-writable. If any file in these directories is found to be group-writable or world-writable, correct its permission with the following command:

    $ sudo chmod go-w FILE

RHEL-06-000046

CCI-001499

medium

Library files must be owned by root.

Files from shared library directories are loaded into the address space of processes (including privileged ones) or of the kernel itself at runtime. Proper ownership is necessary to protect the integrity of the system.

If , this is a finding.

System-wide shared library files, which are linked to executables during process load time or run time, are stored in the following directories by default:

    /lib
    /lib64
    /usr/lib
    /usr/lib64

Kernel modules, which can be added to the kernel during runtime, are also stored in `/lib/modules`. All files in these directories should be owned by the `root` user. If the directory, or any file in these directories, is found to be owned by a user other than root correct its ownership with the following command:

    $ sudo chown root FILE

RHEL-06-000047

CCI-001499

medium

All system command files must have mode 0755 or less permissive.

System binaries are executed by privileged users, as well as system services, and restrictive permissions are necessary to ensure execution of these programs cannot be co-opted.

If , this is a finding.

System executables are stored in the following directories by default:

    /bin
    /sbin
    /usr/bin
    /usr/libexec
    /usr/local/bin
    /usr/local/sbin
    /usr/sbin

All files in these directories should not be group-writable or world-writable. If any file FILE in these directories is found to be group-writable or world-writable, correct its permission with the following command:

    $ sudo chmod go-w FILE

RHEL-06-000048

CCI-001499

medium

All system command files must be owned by root.

System binaries are executed by privileged users as well as system services, and restrictive permissions are necessary to ensure that their execution of these programs cannot be co-opted.

If , this is a finding.

System executables are stored in the following directories by default:

    /bin
    /sbin
    /usr/bin
    /usr/libexec
    /usr/local/bin
    /usr/local/sbin
    /usr/sbin

All files in these directories should be owned by the `root` user. If any file FILE in these directories is found to be owned by a user other than root, correct its ownership with the following command:

    $ sudo chown root FILE

RHEL-06-000050

CCI-000205

medium

The system must require passwords to contain a minimum of 14 characters.

Requiring a minimum password length makes password cracking attacks more difficult by ensuring a larger search space. However, any security benefit from an onerous requirement must be carefully weighed against usability problems, support costs, or counterproductive behavior that may result.

If , this is a finding.

To specify password length requirements for new accounts, edit the file `/etc/login.defs` and add or correct the following lines:

    PASS_MIN_LEN

As of the DISA Red Hat 6 STIG - Ver 1, Rel 13 (28-OCT-2016), the DoD requirement is now `15`. The FISMA requirement is `12`. If a program consults `/etc/login.defs` and also another PAM module (such as `pam_cracklib`) during a password change operation, then the most restrictive must be satisfied. See PAM section for more information about enforcing password quality requirements.

RHEL-06-000051

CCI-000198

medium

Users must not be able to change passwords more than once every 24 hours.

Setting the minimum password age protects against users cycling back to a favorite password after satisfying the password reuse requirement.

If , this is a finding.

To specify password minimum age for new accounts, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_MIN_DAYS

A value of 1 day is considered sufficient for many environments. The DoD requirement is 1.

RHEL-06-000053

CCI-000199

medium

User passwords must be changed at least every 60 days.

Setting the password maximum age ensures users are required to periodically change their passwords. This could possibly decrease the utility of a stolen password. Requiring shorter password lifetimes increases the risk of users writing down the password in a convenient location subject to physical compromise.

If , this is a finding.

To specify password maximum age for new accounts, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_MAX_DAYS

A value of 180 days is sufficient for many environments. The DoD requirement is 60.

RHEL-06-000054

CCI-000366

low

Users must be warned 7 days in advance of password expiration.

Setting the password warning age enables users to make the change at a practical time.

If , this is a finding.

To specify how many days prior to password expiration that a warning will be issued to users, edit the file `/etc/login.defs` and add or correct the following line:

    PASS_WARN_AGE

The DoD requirement is 7.

RHEL-06-000056

CCI-000194

low

The system must require passwords to contain at least one numeric character.

Requiring digits makes password guessing attacks more difficult by ensuring a larger search space.

If , this is a finding.

The pam_cracklib module's `dcredit` parameter controls requirements for usage of digits in a password. When set to a negative number, any password will be required to contain that many digits. When set to a positive number, pam_cracklib will grant +1 additional length credit for each digit. Add `dcredit=-1` after pam_cracklib.so to require use of a digit in passwords.

RHEL-06-000057

CCI-000192

low

The system must require passwords to contain at least one uppercase alphabetic character.

Requiring a minimum number of uppercase characters makes password guessing attacks more difficult by ensuring a larger search space.

If , this is a finding.

The pam_cracklib module's `ucredit=` parameter controls requirements for usage of uppercase letters in a password. When set to a negative number, any password will be required to contain that many uppercase characters. When set to a positive number, pam_cracklib will grant +1 additional length credit for each uppercase character. Add `ucredit=-1` after pam_cracklib.so to require use of an upper case character in passwords.

RHEL-06-000058

CCI-001619

low

The system must require passwords to contain at least one special character.

Requiring a minimum number of special characters makes password guessing attacks more difficult by ensuring a larger search space.

If , this is a finding.

The pam_cracklib module's `ocredit=` parameter controls requirements for usage of special (or ``other'') characters in a password. When set to a negative number, any password will be required to contain that many special characters. When set to a positive number, pam_cracklib will grant +1 additional length credit for each special character. Add `ocredit=` after pam_cracklib.so to require use of a special character in passwords.

RHEL-06-000059

CCI-000193

low

The system must require passwords to contain at least one lowercase alphabetic character.

Requiring a minimum number of lowercase characters makes password guessing attacks more difficult by ensuring a larger search space.

If , this is a finding.

The pam_cracklib module's `lcredit=` parameter controls requirements for usage of lowercase letters in a password. When set to a negative number, any password will be required to contain that many lowercase characters. When set to a positive number, pam_cracklib will grant +1 additional length credit for each lowercase character. Add `lcredit=-1` after pam_cracklib.so to require use of a lowercase character in passwords.

RHEL-06-000060

CCI-000195

low

The system must require at least four characters be changed between the old and new passwords during a password change.

Requiring a minimum number of different characters during password changes ensures that newly changed passwords should not resemble previously compromised ones. Note that passwords which are changed on compromised systems will still be compromised, however.

If , this is a finding.

The pam_cracklib module's `difok` parameter controls requirements for usage of different characters during a password change. Add `difok=` after pam_cracklib.so to require differing characters when changing passwords. The DoD requirement is `4`.

RHEL-06-000061

CCI-000044

medium

The system must disable accounts after three consecutive unsuccessful logon attempts.

Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks.

If , this is a finding.

To configure the system to lock out accounts after a number of incorrect login attempts using `pam_faillock.so`, modify the content of both `/etc/pam.d/system-auth` and `/etc/pam.d/password-auth` as follows:

- Add the following line immediately `before` the `pam_unix.so` statement in the `AUTH` section:

      auth required pam_faillock.so preauth silent deny= unlock_time= fail_interval=

- Add the following line immediately `after` the `pam_unix.so` statement in the `AUTH` section:

      auth [default=die] pam_faillock.so authfail deny= unlock_time= fail_interval=

- Add the following line immediately `before` the `pam_unix.so` statement in the `ACCOUNT` section:

      account required pam_faillock.so

RHEL-06-000062

CCI-000803

medium

The system must use a FIPS 140-2 approved cryptographic hashing algorithm for generating account password hashes (system-auth).

Using a stronger hashing algorithm makes password cracking attacks more difficult.

If , this is a finding.

In `/etc/pam.d/system-auth`, the `password` section of the file controls which PAM modules execute during a password change. Set the `pam_unix.so` module in the `password` section to include the argument `sha512`, as shown below:

    password    sufficient    pam_unix.so sha512 other arguments...

This will help ensure when local users change their passwords, hashes for the new passwords will be generated using the SHA-512 algorithm. This is the default.

RHEL-06-000063

CCI-000803

medium

The system must use a FIPS 140-2 approved cryptographic hashing algorithm for generating account password hashes (login.defs).

Using a stronger hashing algorithm makes password cracking attacks more difficult.

If , this is a finding.

In `/etc/login.defs`, add or correct the following line to ensure the system will use SHA-512 as the hashing algorithm:

    ENCRYPT_METHOD SHA512

RHEL-06-000064

CCI-000803

medium

The system must use a FIPS 140-2 approved cryptographic hashing algorithm for generating account password hashes (libuser.conf).

Using a stronger hashing algorithm makes password cracking attacks more difficult.

If , this is a finding.

In `/etc/libuser.conf`, add or correct the following line in its `[defaults]` section to ensure the system will use the SHA-512 algorithm for password hashing:

    crypt_style = sha512

RHEL-06-000065

CCI-000366

medium

The system boot loader configuration file(s) must be owned by root.

Only root should be able to modify important boot parameters.

If , this is a finding.

The file `/etc/grub.conf` should be owned by the `root` user to prevent destruction or modification of the file. To properly set the owner of `/etc/grub.conf`, run the command:

    $ sudo chown root /etc/grub.conf

RHEL-06-000066

CCI-000366

medium

The system boot loader configuration file(s) must be group-owned by root.

The `root` group is a highly-privileged group. Furthermore, the group-owner of this file should not have any access privileges anyway.

If , this is a finding.

The file `/etc/grub.conf` should be group-owned by the `root` group to prevent destruction or modification of the file. To properly set the group owner of `/etc/grub.conf`, run the command:

    $ sudo chgrp root /etc/grub.conf

RHEL-06-000067

CCI-000366

medium

The system boot loader configuration file(s) must have mode 0600 or less permissive.

Proper permissions ensure that only the root user can modify important boot parameters.

If , this is a finding.

File permissions for `/boot/grub/grub.conf` should be set to 600, which is the default. To properly set the permissions of `/boot/grub/grub.conf`, run the command:

    $ sudo chmod 600 /boot/grub/grub.conf

RHEL-06-000068

CCI-000213

medium

The system boot loader must require authentication.

Password protection on the boot loader configuration ensures users with physical access cannot trivially alter important bootloader settings. These include which kernel to use, and whether to enter single-user mode.

If , this is a finding.

The grub boot loader should have password protection enabled to protect boot-time settings. To do so, select a password and then generate a hash from it by running the following command:

    $ grub-crypt --sha-512

When prompted to enter a password, insert the following line into `/etc/grub.conf` immediately after the header comments. (Use the output from `grub-crypt` as the value of password-hash):

    password --encrypted password-hash

NOTE: To meet FISMA Moderate, the bootloader password MUST differ from the root password.

RHEL-06-000069

CCI-000213

medium

The system must require authentication upon booting into single-user and maintenance modes.

This prevents attackers with physical access from trivially bypassing security on the machine and gaining root access. Such accesses are further prevented by configuring the bootloader password.

If , this is a finding.

Single-user mode is intended as a system recovery method, providing a single user root access to the system by providing a boot option at startup. By default, no authentication is performed if single-user mode is selected.
To require entry of the root password even if the system is started in single-user mode, add or correct the following line in the file `/etc/sysconfig/init`:

    SINGLE=/sbin/sulogin

RHEL-06-000070

CCI-000213

medium

The system must not permit interactive boot.

Using interactive boot, the console user could disable auditing, firewalls, or other services, weakening system security.

If , this is a finding.

To disable the ability for users to perform interactive startups, perform both of the following:

1. Edit the file `/etc/sysconfig/init`. Add or correct the line:

       PROMPT=no

2. Inspect the kernel boot arguments (which follow the word `kernel`) in `/etc/grub.conf` and ensure the `confirm` argument is not present.

Both the `PROMPT` option of the `/etc/sysconfig/init` file and the `confirm` kernel boot argument of the `/etc/grub.conf` file allow the console user to perform an interactive system startup, in which it is possible to select the set of services which are started on boot.

RHEL-06-000071

CCI-000058

low

The system must allow locking of the console screen in text mode.

Installing `screen` ensures a console locking capability is available for users who may need to suspend console logins.

If , this is a finding.

To enable console screen locking, install the `screen` package:

    $ sudo yum install screen

Instruct users to begin new terminal sessions with the following command:

    $ screen

The console can now be locked with the following key combination:

    ctrl+a x

RHEL-06-000073

CCI-NaN

medium

The Department of Defense (DoD) login banner must be displayed immediately prior to, or as part of, console login prompts.

An appropriate warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers.

If , this is a finding.

To configure the system login banner:
Edit `/etc/issue`. Replace the default text with a message compliant with the local site policy or a legal disclaimer. The DoD required text is either:
`You are accessing a U.S. Government (USG) Information System (IS) that is provided for USG-authorized use only. By using this IS (which includes any device attached to this IS), you consent to the following conditions:
-The USG routinely intercepts and monitors communications on this IS for purposes including, but not limited to, penetration testing, COMSEC monitoring, network operations and defense, personnel misconduct (PM), law enforcement (LE), and counterintelligence (CI) investigations.
-At any time, the USG may inspect and seize data stored on this IS.
-Communications using, or data stored on, this IS are not private, are subject to routine monitoring, interception, and search, and may be disclosed or used for any USG-authorized purpose.
-This IS includes security measures (e.g., authentication and access controls) to protect USG interests -- not for your personal benefit or privacy.
-Notwithstanding the above, using this IS does not constitute consent to PM, LE or CI investigative searching or monitoring of the content of privileged communications, or work product, related to personal representation or services by attorneys, psychotherapists, or clergy, and their assistants. Such communications and work product are private and confidential. See User Agreement for details.`
OR:
`Use of this or any other DoD interest computer system constitutes consent to monitoring at all times.
This is a DoD interest computer system. All DoD interest computer systems and related equipment are intended for the communication, transmission, processing, and storage of official U.S. Government or other authorized information only. All DoD interest computer systems are subject to monitoring at all times to ensure proper functioning of equipment and systems including security devices and systems, to prevent unauthorized use and violations of statutes and security regulations, to deter criminal activity, and for other similar purposes. Any user of a DoD interest computer system should be aware that any information placed in the system is subject to monitoring and is not subject to any expectation of privacy.
If monitoring of this or any other DoD interest computer system reveals possible evidence of violation of criminal statutes, this evidence and any other related information, including identification information about the user, may be provided to law enforcement officials. If monitoring of this or any other DoD interest computer systems reveals violations of security regulations or unauthorized use, employees who violate security regulations or make unauthorized use of DoD interest computer systems are subject to appropriate disciplinary action.
Use of this or any other DoD interest computer system constitutes consent to monitoring at all times.`
OR:
`I've read & consent to terms in IS user agreem't.`

RHEL-06-000078

CCI-000366

medium

The system must implement virtual address space randomization.

Address space layout randomization (ASLR) makes it more difficult for an attacker to predict the location of attack code they have introduced into a process's address space during an attempt at exploitation. Additionally, ASLR makes it more difficult for an attacker to know the location of existing code in order to re-purpose it using return oriented programming (ROP) techniques.

If , this is a finding.

To set the runtime status of the `kernel.randomize_va_space` kernel parameter, run the following command:

    $ sudo sysctl -w kernel.randomize_va_space=2

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    kernel.randomize_va_space = 2

RHEL-06-000079

CCI-000366

medium

The system must limit the ability of processes to have simultaneous write and execute access to memory.

ExecShield uses the segmentation feature on all x86 systems to prevent execution in memory higher than a certain address. It writes an address as a limit in the code segment descriptor, to control where code can be executed, on a per-process basis. When the kernel places a process's memory regions such as the stack and heap higher than this address, the hardware prevents execution in that address range.

If , this is a finding.

To set the runtime status of the `kernel.exec-shield` kernel parameter, run the following command:

    $ sudo sysctl -w kernel.exec-shield=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    kernel.exec-shield = 1

RHEL-06-000080

CCI-000366

medium

The system must not send ICMPv4 redirects by default.

Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.default.send_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.send_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.default.send_redirects = 0

RHEL-06-000081

CCI-000366

medium

The system must not send ICMPv4 redirects from any interface.

Sending ICMP redirects permits the system to instruct other systems to update their routing information. The ability to send ICMP redirects is only appropriate for systems acting as routers.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.send_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.send_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.send_redirects = 0

RHEL-06-000082

CCI-000366

medium

IP forwarding for IPv4 must not be enabled, unless the system is a router.

IP forwarding permits the kernel to forward packets from one network interface to another. The ability to forward packets between two networks is only appropriate for systems acting as routers.

If , this is a finding.

To set the runtime status of the `net.ipv4.ip_forward` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.ip_forward=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.ip_forward = 0

RHEL-06-000083

CCI-000366

medium

The system must not accept IPv4 source-routed packets on any interface.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.accept_source_route=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.accept_source_route = 0

RHEL-06-000084

CCI-000366

medium

The system must not accept ICMPv4 redirect packets on any interface.

Accepting ICMP redirects has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.accept_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.accept_redirects = 0

RHEL-06-000086

CCI-000366

medium

The system must not accept ICMPv4 secure redirect packets on any interface.

Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.secure_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.secure_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.secure_redirects = 0

RHEL-06-000088

CCI-000366

low

The system must log Martian packets.

The presence of "martian" packets (which have impossible addresses) as well as spoofed packets, source-routed packets, and redirects could be a sign of nefarious network activity. Logging these packets enables this activity to be detected.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.log_martians` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.log_martians=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.log_martians = 1

RHEL-06-000089

CCI-000366

medium

The system must not accept IPv4 source-routed packets by default.

Accepting source-routed packets in the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.default.accept_source_route` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.accept_source_route=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.default.accept_source_route = 0

RHEL-06-000090

CCI-000366

medium

The system must not accept ICMPv4 secure redirect packets by default.

Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.default.secure_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.secure_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.default.secure_redirects = 0

RHEL-06-000091

CCI-000366

low

The system must ignore ICMPv4 redirect messages by default.

This feature of the IPv4 protocol has few legitimate uses. It should be disabled unless it is absolutely required.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.default.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.accept_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.default.accept_redirects = 0

RHEL-06-000092

CCI-000366

low

The system must not respond to ICMPv4 sent to a broadcast address.

Ignoring ICMP echo requests (pings) sent to broadcast or multicast addresses makes the system slightly more difficult to enumerate on the network.

If , this is a finding.

To set the runtime status of the `net.ipv4.icmp_echo_ignore_broadcasts` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.icmp_echo_ignore_broadcasts=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.icmp_echo_ignore_broadcasts = 1

RHEL-06-000093

CCI-000366

low

The system must ignore ICMPv4 bogus error responses.

Ignoring bogus ICMP error responses reduces log size, although some activity would not be logged.

If , this is a finding.

To set the runtime status of the `net.ipv4.icmp_ignore_bogus_error_responses` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_responses=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.icmp_ignore_bogus_error_responses = 1

RHEL-06-000095

CCI-001095

medium

The system must be configured to use TCP syncookies.

A TCP SYN flood attack can cause a denial of service by filling a system's TCP connection table with connections in the SYN_RCVD state. Syncookies can be used to track a connection when a subsequent ACK is received, verifying the initiator is attempting a valid connection and is not a flood source. This feature is activated when a flood condition is detected, and enables the system to continue servicing valid connection requests.

If , this is a finding.

To set the runtime status of the `net.ipv4.tcp_syncookies` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.tcp_syncookies=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.tcp_syncookies = 1

RHEL-06-000096

CCI-000366

medium

The system must use a reverse-path filter for IPv4 network traffic when possible on all interfaces.

Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.all.rp_filter` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.all.rp_filter=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.all.rp_filter = 1

RHEL-06-000097

CCI-000366

medium

The system must use a reverse-path filter for IPv4 network traffic when possible by default.

Enabling reverse path filtering drops packets with source addresses that should not have been able to be received on the interface they were received on. It should not be used on systems which are routers for complicated networks, but is helpful for end hosts and routers serving small networks.

If , this is a finding.

To set the runtime status of the `net.ipv4.conf.default.rp_filter` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv4.conf.default.rp_filter=1

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv4.conf.default.rp_filter = 1

RHEL-06-000098

CCI-000366

medium

The IPv6 protocol handler must not be bound to the network stack unless needed.

Any unnecessary network stacks - including IPv6 - should be disabled, to reduce the vulnerability to exploitation.

If , this is a finding.

To prevent the IPv6 kernel module (`ipv6`) from binding to the IPv6 networking stack, add the following line to `/etc/modprobe.d/disabled.conf` (or another file in `/etc/modprobe.d`):

    options ipv6 disable=1

This permits the IPv6 module to be loaded (and thus satisfy other modules that depend on it), while disabling support for the IPv6 protocol.

RHEL-06-000099

CCI-000366

medium

The system must ignore ICMPv6 redirects by default.

An illicit ICMP redirect message could result in a man-in-the-middle attack.

If , this is a finding.

To set the runtime status of the `net.ipv6.conf.default.accept_redirects` kernel parameter, run the following command:

    $ sudo sysctl -w net.ipv6.conf.default.accept_redirects=0

If this is not the system's default value, add the following line to `/etc/sysctl.conf`:

    net.ipv6.conf.default.accept_redirects = 0

RHEL-06-000103

CCI-001118

medium

The system must employ a local IPv6 firewall.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000105

CCI-001117

medium

The system must employ a local IPv6 firewall.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000106

CCI-001098

medium

The operating system must connect to external networks or information systems only through managed IPv6 interfaces consisting of boundary protection devices arranged in accordance with an organizational security architecture.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000107

CCI-001100

medium

The operating system must prevent public IPv6 access into an organizations internal networks, except as appropriately mediated by managed interfaces employing boundary protection devices.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000108

CCI-001097

medium

The system must employ a local IPv6 firewall.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000109

CCI-001414

medium

The system must employ a local IPv6 firewall.

The `ip6tables` service provides the system's host-based firewalling capability for IPv6 and ICMPv6.

If , this is a finding.

The `ip6tables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ip6tables on

RHEL-06-000113

CCI-001118

medium

The system must employ a local IPv4 firewall.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000115

CCI-001117

medium

The system must employ a local IPv4 firewall.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000116

CCI-001098

medium

The operating system must connect to external networks or information systems only through managed IPv4 interfaces consisting of boundary protection devices arranged in accordance with an organizational security architecture.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000117

CCI-001100

medium

The operating system must prevent public IPv4 access into an organizations internal networks, except as appropriately mediated by managed interfaces employing boundary protection devices.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000118

CCI-001097

medium

The system must employ a local IPv4 firewall.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000119

CCI-001414

medium

The system must employ a local IPv4 firewall.

The `iptables` service provides the system's host-based firewalling capability for IPv4 and ICMP.

If , this is a finding.

The `iptables` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 iptables on

RHEL-06-000120

CCI-000066

medium

The systems local IPv4 firewall must implement a deny-all, allow-by-exception policy for inbound packets.

In `iptables` the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

If , this is a finding.

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/sysconfig/iptables`:

    :INPUT DROP [0:0]

RHEL-06-000121

CCI-001115

medium

The system's local firewall must implement a deny-all, allow-by-exception policy for inbound packets.

In `iptables` the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

If , this is a finding.

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/sysconfig/iptables`:

    :INPUT DROP [0:0]

RHEL-06-000122

CCI-001154

medium

The system's local firewall must implement a deny-all, allow-by-exception policy for inbound packets.

In `iptables` the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

If , this is a finding.

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/sysconfig/iptables`:

    :INPUT DROP [0:0]

RHEL-06-000124

CCI-000382

medium

The Datagram Congestion Control Protocol (DCCP) must be disabled unless required.

Disabling DCCP protects the system against exploitation of any flaws in its implementation.

If , this is a finding.

The Datagram Congestion Control Protocol (DCCP) is a relatively new transport layer protocol, designed to support streaming media and telephony. To configure the system to prevent the `dccp` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install dccp /bin/true

RHEL-06-000125

CCI-000382

medium

The Stream Control Transmission Protocol (SCTP) must be disabled unless required.

Disabling SCTP protects the system against exploitation of any flaws in its implementation.

If , this is a finding.

The Stream Control Transmission Protocol (SCTP) is a transport layer protocol, designed to support the idea of message-oriented communication, with several streams of messages within one connection. To configure the system to prevent the `sctp` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install sctp /bin/true

RHEL-06-000126

CCI-000382

low

The Reliable Datagram Sockets (RDS) protocol must be disabled unless required.

Disabling RDS protects the system against exploitation of any flaws in its implementation.

If , this is a finding.

The Reliable Datagram Sockets (RDS) protocol is a transport layer protocol designed to provide reliable high- bandwidth, low-latency communications between nodes in a cluster. To configure the system to prevent the `rds` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install rds /bin/true

RHEL-06-000127

CCI-000382

medium

The Transparent Inter-Process Communication (TIPC) protocol must be disabled unless required.

Disabling TIPC protects the system against exploitation of any flaws in its implementation.

If , this is a finding.

The Transparent Inter-Process Communication (TIPC) protocol is designed to provide communications between nodes in a cluster. To configure the system to prevent the `tipc` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install tipc /bin/true

RHEL-06-000133

CCI-001314

medium

All rsyslog-generated log files must be owned by root.

The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.

If , this is a finding.

The owner of all log files written by `rsyslog` should be root. These log files are determined by the second part of each Rule line in `/etc/rsyslog.conf` and typically all appear in `/var/log`. For each log file LOGFILE referenced in `/etc/rsyslog.conf`, run the following command to inspect the file's owner:

    $ ls -l LOGFILE

If the owner is not `root`, run the following command to correct this:

    $ sudo chown root LOGFILE

RHEL-06-000134

CCI-001314

medium

All rsyslog-generated log files must be group-owned by root.

The log files generated by rsyslog contain valuable information regarding system configuration, user authentication, and other such information. Log files should be protected from unauthorized access.

If , this is a finding.

The group-owner of all log files written by `rsyslog` should be root. These log files are determined by the second part of each Rule line in `/etc/rsyslog.conf` and typically all appear in `/var/log`. For each log file LOGFILE referenced in `/etc/rsyslog.conf`, run the following command to inspect the file's group owner:

    $ ls -l LOGFILE

If the owner is not `root`, run the following command to correct this:

    $ sudo chgrp root LOGFILE

RHEL-06-000135

CCI-001314

medium

All rsyslog-generated log files must have mode 0600 or less permissive.

Log files can contain valuable information regarding system configuration. If the system log files are not protected unauthorized users could change the logged data, eliminating their forensic value.

If , this is a finding.

The file permissions for all log files written by `rsyslog` should be set to 600, or more restrictive. These log files are determined by the second part of each Rule line in `/etc/rsyslog.conf` and typically all appear in `/var/log`. For each log file LOGFILE referenced in `/etc/rsyslog.conf`, run the following command to inspect the file's permissions:

    $ ls -l LOGFILE

If the permissions are not 600 or more restrictive, run the following command to correct this:

    $ sudo chmod 0600 LOGFILE

RHEL-06-000136

CCI-001348

medium

The operating system must back up audit records on an organization defined frequency onto a different system or media than the system being audited.

A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise.

If , this is a finding.

To configure rsyslog to send logs to a remote log server, open `/etc/rsyslog.conf` and read and understand the last section of the file, which describes the multiple directives necessary to activate remote logging. Along with these other directives, the system can be configured to forward its logs to a particular log server by adding or correcting one of the following lines, substituting `loghost.example.com` appropriately. The choice of protocol depends on the environment of the system; although TCP and RELP provide more reliable message delivery, they may not be supported in all environments.
To use UDP for log message delivery:

    *.* @loghost.example.com

To use TCP for log message delivery:

    *.* @@loghost.example.com

To use RELP for log message delivery:

    *.* :omrelp:loghost.example.com

RHEL-06-000137

CCI-000169

medium

The operating system must support the requirement to centrally manage the content of audit records generated by organization defined information system components.

A log server (loghost) receives syslog messages from one or more systems. This data can be used as an additional log source in the event a system is compromised and its local logs are suspect. Forwarding log messages to a remote loghost also provides system administrators with a centralized place to view the status of multiple hosts within the enterprise.

If , this is a finding.

To configure rsyslog to send logs to a remote log server, open `/etc/rsyslog.conf` and read and understand the last section of the file, which describes the multiple directives necessary to activate remote logging. Along with these other directives, the system can be configured to forward its logs to a particular log server by adding or correcting one of the following lines, substituting `loghost.example.com` appropriately. The choice of protocol depends on the environment of the system; although TCP and RELP provide more reliable message delivery, they may not be supported in all environments.
To use UDP for log message delivery:

    *.* @loghost.example.com

To use TCP for log message delivery:

    *.* @@loghost.example.com

To use RELP for log message delivery:

    *.* :omrelp:loghost.example.com

RHEL-06-000138

CCI-000366

low

System logs must be rotated daily.

Log files that are not properly rotated run the risk of growing so large that they fill up the /var/log partition. Valuable logging information could be lost if the /var/log partition becomes full.

If , this is a finding.

The `logrotate` utility allows for the automatic rotation of log files. The frequency of rotation is specified in `/etc/logrotate.conf`, which triggers a cron task. To configure logrotate to run daily, add or correct the following line in `/etc/logrotate.conf`:

    # rotate log files frequency
    daily

RHEL-06-000139

CCI-000347

medium

Auditing must be implemented.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000142

CCI-000880

medium

The operating system must audit nonlocal maintenance and diagnostic sessions.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000143

CCI-001353

medium

The operating system must produce a system-wide (logical or physical) audit trail composed of audit records in a standardized format.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000145

CCI-001487

medium

The operating system must produce audit records containing sufficient information to establish the identity of any user/subject associated with the event.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000148

CCI-000067

medium

The operating system must employ automated mechanisms to facilitate the monitoring and control of remote access methods.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000149

CCI-000158

medium

The operating system must provide the capability to automatically process audit records for events of interest based upon selectable, event criteria.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000151

CCI-001190

medium

The operating system must fail to an organization defined known state for organization defined types of failures.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000154

CCI-000130

medium

The operating system must produce audit records containing sufficient information to establish what type of events occurred.

Ensuring the `auditd` service is active ensures audit records generated by the kernel can be written to disk, or that appropriate actions will be taken if other obstacles exist.

If , this is a finding.

The `auditd` service is an essential userspace component of the Linux Auditing System, as it is responsible for writing audit records to disk. The `auditd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 auditd on

RHEL-06-000157

CCI-001464

low

Auditing must be enabled at boot by setting a kernel parameter.

Each process on the system carries an "auditable" flag which indicates whether its activities can be audited. Although `auditd` takes care of enabling this for all processes which launch after it does, adding the kernel argument ensures it is set for every process during boot.

If , this is a finding.

To ensure all processes can be audited, even those which start prior to the audit daemon, add the argument `audit=1` to the kernel line in `/etc/grub.conf`, in the manner below:

    kernel /vmlinuz-version ro vga=ext root=/dev/VolGroup00/LogVol00 rhgb quiet audit=1

RHEL-06-000159

CCI-000366

medium

The system must retain enough rotated audit logs to cover the required log retention period.

The total storage for audit log files must be large enough to retain log information over the period required. This is a function of the maximum log file size and the number of logs retained.

If , this is a finding.

Determine how many log files `auditd` should retain when it rotates logs. Edit the file `/etc/audit/auditd.conf`. Add or modify the following line, substituting NUMLOGS with the correct value of :

    num_logs = NUMLOGS

Set the value to 5 for general-purpose systems. Note that values less than 2 result in no log rotation.

RHEL-06-000160

CCI-000366

medium

The system must set a maximum audit log file size.

The total storage for audit log files must be large enough to retain log information over the period required. This is a function of the maximum log file size and the number of logs retained.

If , this is a finding.

Determine the amount of audit data (in megabytes) which should be retained in each log file. Edit the file `/etc/audit/auditd.conf`. Add or modify the following line, substituting the correct value of for STOREMB:

    max_log_file = STOREMB

Set the value to `6` (MB) or higher for general-purpose systems. Larger values, of course, support retention of even more audit data.

RHEL-06-000161

CCI-000366

medium

The system must rotate audit log files that reach the maximum file size.

Automatically rotating logs (by setting this to `rotate`) minimizes the chances of the system unexpectedly running out of disk space by being overwhelmed with log data. However, for systems that must never discard log data, or which use external processes to transfer it and reclaim space, `keep_logs` can be employed.

If , this is a finding.

The default action to take when the logs reach their maximum size is to rotate the log files, discarding the oldest one. To configure the action taken by `auditd`, add or correct the line in `/etc/audit/auditd.conf`:

    max_log_file_action = ACTION

Possible values for ACTION are described in the `auditd.conf` man page. These include:

- `ignore`
- `syslog`
- `suspend`
- `rotate`
- `keep_logs`

Set the `ACTION` to `rotate` to ensure log rotation occurs. This is the default. The setting is case-insensitive.

RHEL-06-999999

CCI-000366

medium

The audit system must switch the system to single-user mode when available audit storage volume becomes dangerously low.

Administrators should be made aware of an inability to record audit records. If a separate partition or logical volume of adequate size is used, running low on space for audit records should never occur.

If , this is a finding.

The `auditd` service can be configured to take an action when disk space is running low but prior to running out of space completely. Edit the file `/etc/audit/auditd.conf`. Add or modify the following line, substituting ACTION appropriately:

    admin_space_left_action = ACTION

Set this value to `single` to cause the system to switch to single-user mode for corrective action. Acceptable values also include `suspend` and `halt`. For certain systems, the need for availability outweighs the need to log all actions, and a different setting should be determined. Details regarding all possible values for ACTION are described in the `auditd.conf` man page.

RHEL-06-000165

CCI-000169

low

The audit system must be configured to audit all attempts to alter system time through adjtimex.

Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.

If , this is a finding.

On a 32-bit system, add the following to `/etc/audit/audit.rules`:

    # audit_time_rules
    -a always,exit -F arch=b32 -S adjtimex -k audit_time_rules

On a 64-bit system, add the following to `/etc/audit/audit.rules`:

    # audit_time_rules
    -a always,exit -F arch=b64 -S adjtimex -k audit_time_rules

The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:

    -a always,exit -F arch=b64 -S adjtimex -S settimeofday -k audit_time_rules

RHEL-06-000167

CCI-000169

low

The audit system must be configured to audit all attempts to alter system time through settimeofday.

Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.

If , this is a finding.

On a 32-bit system, add the following to `/etc/audit/audit.rules`:

    # audit_time_rules
    -a always,exit -F arch=b32 -S settimeofday -k audit_time_rules

On a 64-bit system, add the following to `/etc/audit/audit.rules`:

    # audit_time_rules
    -a always,exit -F arch=b64 -S settimeofday -k audit_time_rules

The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:

    -a always,exit -F arch=b64 -S adjtimex -S settimeofday -k audit_time_rules

RHEL-06-000169

CCI-000169

low

The audit system must be configured to audit all attempts to alter system time through stime.

Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.

If , this is a finding.

Add the following line to `/etc/audit/audit.rules` for both 32-bit and 64-bit systems:

    # audit_time_rules
    -a always,exit -F arch=b32 -S stime -k audit_time_rules

Since the 64-bit version of the "stime" system call is not defined in the audit lookup table, the corresponding "-F arch=b64" form of this rule is not expected to be defined on 64-bit systems (the aforementioned "-F arch=b32" stime rule form itself is sufficient for both 32-bit and 64-bit systems). The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:

    -a always,exit -F arch=b64 -S adjtimex -S settimeofday -k audit_time_rules

RHEL-06-000171

CCI-000169

low

The audit system must be configured to audit all attempts to alter system time through clock_settime.

Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.

If , this is a finding.

On a 32-bit system, add the following to `/etc/audit/audit.rules`:

    # time-change
    -a always,exit -F arch=b32 -S clock_settime -F a0=0x0 -F key=time-change

On a 64-bit system, add the following to `/etc/audit/audit.rules`:

    # time-change
    -a always,exit -F arch=b64 -S clock_settime -F a0=0x0 -F key=time-change

The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport. Multiple system calls can be defined on the same line to save space if desired, but is not required. See an example of multiple combined syscalls:

    -a always,exit -F arch=b64 -S adjtimex -S settimeofday -k audit_time_rules

RHEL-06-000173

CCI-000169

low

The audit system must be configured to audit all attempts to alter system time through /etc/localtime.

Arbitrary changes to the system time can be used to obfuscate nefarious activities in log files, as well as to confuse network services that are highly dependent upon an accurate system time (such as sshd). All changes to the system time should be audited.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`:

    -w /etc/localtime -p wa -k audit_time_rules

The -k option allows for the specification of a key in string form that can be used for better reporting capability through ausearch and aureport and should always be used.

RHEL-06-000174

CCI-000018

low

The operating system must automatically audit account creation.

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`, in order to capture events that modify account changes:

    # audit_rules_usergroup_modification
    -w /etc/group -p wa -k audit_rules_usergroup_modification
    -w /etc/passwd -p wa -k audit_rules_usergroup_modification
    -w /etc/gshadow -p wa -k audit_rules_usergroup_modification
    -w /etc/shadow -p wa -k audit_rules_usergroup_modification
    -w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

RHEL-06-000175

CCI-001403

low

The operating system must automatically audit account modification.

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`, in order to capture events that modify account changes:

    # audit_rules_usergroup_modification
    -w /etc/group -p wa -k audit_rules_usergroup_modification
    -w /etc/passwd -p wa -k audit_rules_usergroup_modification
    -w /etc/gshadow -p wa -k audit_rules_usergroup_modification
    -w /etc/shadow -p wa -k audit_rules_usergroup_modification
    -w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

RHEL-06-000176

CCI-001404

low

The operating system must automatically audit account disabling actions.

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`, in order to capture events that modify account changes:

    # audit_rules_usergroup_modification
    -w /etc/group -p wa -k audit_rules_usergroup_modification
    -w /etc/passwd -p wa -k audit_rules_usergroup_modification
    -w /etc/gshadow -p wa -k audit_rules_usergroup_modification
    -w /etc/shadow -p wa -k audit_rules_usergroup_modification
    -w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

RHEL-06-000177

CCI-001405

low

The operating system must automatically audit account termination.

In addition to auditing new user and group accounts, these watches will alert the system administrator(s) to any modifications. Any unexpected users, groups, or modifications should be investigated for legitimacy.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`, in order to capture events that modify account changes:

    # audit_rules_usergroup_modification
    -w /etc/group -p wa -k audit_rules_usergroup_modification
    -w /etc/passwd -p wa -k audit_rules_usergroup_modification
    -w /etc/gshadow -p wa -k audit_rules_usergroup_modification
    -w /etc/shadow -p wa -k audit_rules_usergroup_modification
    -w /etc/security/opasswd -p wa -k audit_rules_usergroup_modification

RHEL-06-000182

CCI-000366

low

The audit system must be configured to audit modifications to the systems network configuration.

The network environment should not be modified by anything other than administrator action. Any change to network parameters should be audited.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`, setting ARCH to either b32 or b64 as appropriate for your system:

    # audit_rules_networkconfig_modification
    -a always,exit -F arch=ARCH -S sethostname -S setdomainname -k audit_rules_networkconfig_modification
    -w /etc/issue -p wa -k audit_rules_networkconfig_modification
    -w /etc/issue.net -p wa -k audit_rules_networkconfig_modification
    -w /etc/hosts -p wa -k audit_rules_networkconfig_modification
    -w /etc/sysconfig/network -p wa -k audit_rules_networkconfig_modification

RHEL-06-000183

CCI-000366

low

The audit system must be configured to audit modifications to the systems Mandatory Access Control (MAC) configuration (SELinux).

The system's mandatory access policy (SELinux) should not be arbitrarily changed by anything other than administrator action. All changes to MAC policy should be audited.

If , this is a finding.

Add the following to `/etc/audit/audit.rules`:

    -w /etc/selinux/ -p wa -k MAC-policy

RHEL-06-000184

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using chmod.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S chmod -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S chmod  -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000185

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using chown.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S chown -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S chown -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000186

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fchmod.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fchmod -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fchmod -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000187

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fchmodat.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fchmodat -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000188

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fchown.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fchown -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fchown -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000189

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fchownat.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fchownat -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fchownat -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000190

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fremovexattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000191

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using fsetxattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S fsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S fsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000192

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using lchown.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S lchown -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000193

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using lremovexattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S lremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S lremovexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000194

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using lsetxattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S lsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S lsetxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000195

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using removexattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S removexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S removexattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000196

CCI-000172

low

The audit system must be configured to audit all discretionary access control permission modifications using setxattr.

The changing of file permissions could indicate that a user is attempting to gain access to information that would otherwise be disallowed. Auditing DAC modifications can facilitate the identification of patterns of abuse among both authorized and unauthorized users.

If , this is a finding.

At a minimum the audit system should collect file permission changes for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S setxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S setxattr -F auid>=500 -F auid!=4294967295 -k perm_mod

RHEL-06-000197

CCI-000172

low

The audit system must be configured to audit failed attempts to access files and programs.

Unsuccessful attempts to access files could be an indicator of malicious activity on a system. Auditing these events could serve as evidence of potential system compromise.

If , this is a finding.

At a minimum the audit system should collect unauthorized file accesses for all users and root. Add the following to `/etc/audit/audit.rules`:

    -a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
    -a always,exit -F arch=b32 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access

If the system is 64 bit then also add the following:

    -a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EACCES -F auid>=500 -F auid!=4294967295 -k access
    -a always,exit -F arch=b64 -S creat -S open -S openat -S open_by_handle_at -S truncate -S ftruncate -F exit=-EPERM -F auid>=500 -F auid!=4294967295 -k access

RHEL-06-000198

CCI-000040

low

The audit system must be configured to audit all use of setuid and setgid programs.

Privileged programs are subject to escalation-of-privilege attacks, which attempt to subvert their normal role of providing some necessary but limited capability. As such, motivation exists to monitor these programs for unusual activity.

If , this is a finding.

At a minimum the audit system should collect the execution of privileged commands for all users and root. To find the relevant setuid / setgid programs, run the following command for each local partition PART:

    $ sudo find PART -xdev -type f -perm -4000 -o -type f -perm -2000 2>/dev/null

Then, for each setuid / setgid program on the system, add a line of the following form to `/etc/audit/audit.rules`, where SETUID_PROG_PATH is the full path to each setuid / setgid program in the list:

    -a always,exit -F path=SETUID_PROG_PATH -F perm=x -F auid>=500 -F auid!=4294967295 -k privileged

RHEL-06-000199

CCI-000172

low

The audit system must be configured to audit successful file system mounts.

The unauthorized exportation of data to external media could result in an information leak where classified information, Privacy Act information, and intellectual property could be lost. An audit trail should be created each time a filesystem is mounted to help identify and guard against information loss.

If , this is a finding.

At a minimum the audit system should collect media exportation events for all users and root. Add the following to `/etc/audit/audit.rules`, setting ARCH to either b32 or b64 as appropriate for your system:

    -a always,exit -F arch=ARCH -S mount -F auid>=500 -F auid!=4294967295 -k export

RHEL-06-000200

CCI-000172

low

The audit system must be configured to audit user deletions of files and programs.

Auditing file deletions will create an audit trail for files that are removed from the system. The audit trail could aid in system troubleshooting, as well as, detecting malicious processes that attempt to delete log files to conceal their presence.

If , this is a finding.

At a minimum the audit system should collect file deletion events for all users and root. Add the following to `/etc/audit/audit.rules`, setting ARCH to either b32 or b64 as appropriate for your system:

    -a always,exit -F arch=ARCH -S rmdir -S unlink -S unlinkat -S rename -S renameat -F auid>=500 -F auid!=4294967295 -k delete

RHEL-06-000201

CCI-000172

low

The audit system must be configured to audit changes to the /etc/sudoers file.

The actions taken by system administrators should be audited to keep a record of what was executed on the system, as well as, for accountability purposes.

If , this is a finding.

At a minimum the audit system should collect administrator actions for all users and root. Add the following to `/etc/audit/audit.rules`:

    -w /etc/sudoers -p wa -k actions

RHEL-06-000202

CCI-000172

medium

The audit system must be configured to audit the loading and unloading of dynamic kernel modules.

The addition/removal of kernel modules can be used to alter the behavior of the kernel and potentially introduce malicious code into kernel space. It is important to have an audit trail of modules that have been introduced into the kernel.

If , this is a finding.

Add the following to `/etc/audit/audit.rules` in order to capture kernel module loading and unloading events, setting ARCH to either b32 or b64 as appropriate for your system:

    -w /sbin/insmod -p x -k modules
    -w /sbin/rmmod -p x -k modules
    -w /sbin/modprobe -p x -k modules
    -a always,exit -F arch=ARCH -S init_module -S delete_module -k modules

RHEL-06-000203

CCI-000382

medium

The xinetd service must be disabled if no network services utilizing it are enabled.

The xinetd service provides a dedicated listener service for some programs, which is no longer necessary for commonly-used network services. Disabling it ensures that these uncommon services are not running, and also prevents attacks against xinetd itself.

If , this is a finding.

The `xinetd` service can be disabled with the following command:

    $ sudo chkconfig xinetd off

RHEL-06-000204

CCI-000382

low

The xinetd service must be uninstalled if no network services utilizing it are enabled.

Removing the `xinetd` package decreases the risk of the xinetd service's accidental (or intentional) activation.

If , this is a finding.

The `xinetd` package can be uninstalled with the following command:

    $ sudo yum erase xinetd

RHEL-06-000206

CCI-000381

high

The telnet-server package must not be installed.

Removing the `telnet-server` package decreases the risk of the telnet service's accidental (or intentional) activation.

If , this is a finding.

The `telnet-server` package can be uninstalled with the following command:

    $ sudo yum erase telnet-server

RHEL-06-000211

CCI-000888

high

The telnet daemon must not be running.

The telnet protocol uses unencrypted network communication, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network. The telnet protocol is also subject to man-in-the-middle attacks.

If , this is a finding.

The `telnet` service can be disabled with the following command:

    $ sudo chkconfig telnet off

RHEL-06-000213

CCI-000381

high

The rsh-server package must not be installed.

The `rsh-server` package provides several obsolete and insecure network services. Removing it decreases the risk of those services' accidental (or intentional) activation.

If , this is a finding.

The `rsh-server` package can be uninstalled with the following command:

    $ sudo yum erase rsh-server

RHEL-06-000214

CCI-000068

high

The rshd service must not be running.

The rsh service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.

If , this is a finding.

The `rsh` service, which is available with the `rsh-server` package and runs as a service through xinetd, should be disabled. The `rsh` service can be disabled with the following command:

    $ sudo chkconfig rsh off

RHEL-06-000216

CCI-000068

high

The rexecd service must not be running.

The rexec service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.

If , this is a finding.

The `rexec` service, which is available with the `rsh-server` package and runs as a service through xinetd, should be disabled. The `rexec` service can be disabled with the following command:

    $ sudo chkconfig rexec off

RHEL-06-000218

CCI-001436

high

The rlogind service must not be running.

The rlogin service uses unencrypted network communications, which means that data from the login session, including passwords and all other information transmitted during the session, can be stolen by eavesdroppers on the network.

If , this is a finding.

The `rlogin` service, which is available with the `rsh-server` package and runs as a service through xinetd, should be disabled. The `rlogin` service can be disabled with the following command:

    $ sudo chkconfig rlogin off

RHEL-06-000220

CCI-000381

medium

The ypserv package must not be installed.

Removing the `ypserv` package decreases the risk of the accidental (or intentional) activation of NIS or NIS+ services.

If , this is a finding.

The `ypserv` package can be uninstalled with the following command:

    $ sudo yum erase ypserv

RHEL-06-000221

CCI-000382

medium

The ypbind service must not be running.

Disabling the `ypbind` service ensures the system is not acting as a client in a NIS or NIS+ domain.

If , this is a finding.

The `ypbind` service, which allows the system to act as a client in a NIS or NIS+ domain, should be disabled. The `ypbind` service can be disabled with the following command:

    $ sudo chkconfig ypbind off

RHEL-06-000222

CCI-000381

medium

The tftp-server package must not be installed.

Removing the `tftp-server` package decreases the risk of the accidental (or intentional) activation of tftp services.

If , this is a finding.

The `tftp-server` package can be removed with the following command:

    $ sudo yum erase tftp-server

RHEL-06-000223

CCI-001436

medium

The TFTP service must not be running.

Disabling the `tftp` service ensures the system is not acting as a TFTP server, which does not provide encryption or authentication.

If , this is a finding.

The `tftp` service should be disabled. The `tftp` service can be disabled with the following command:

    $ sudo chkconfig tftp off

RHEL-06-000224

CCI-000366

medium

The cron service must be running.

Due to its usage for maintenance and security-supporting tasks, enabling the cron daemon is essential.

If , this is a finding.

The `crond` service is used to execute commands at preconfigured times. It is required by almost all systems to perform necessary maintenance tasks, such as notifying root of system activity. The `crond` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 crond on

RHEL-06-000227

CCI-000774

high

The SSH daemon must be configured to use only the SSHv2 protocol.

SSH protocol version 1 suffers from design flaws that result in security vulnerabilities and should not be used.

If , this is a finding.

Only SSH protocol version 2 connections should be permitted. The default setting in `/etc/ssh/sshd_config` is correct, and can be verified by ensuring that the following line appears:

    Protocol 2

RHEL-06-000230

CCI-001133

low

The SSH daemon must set a timeout interval on idle sessions.

Causing idle users to be automatically logged out guards against compromises one system leading trivially to compromises on another.

If , this is a finding.

SSH allows administrators to set an idle timeout interval. After this interval has passed, the idle user will be automatically logged out.
To set an idle timeout interval, edit the following line in `/etc/ssh/sshd_config` as follows:

    ClientAliveInterval

The timeout interval is given in seconds. To have a timeout of 15 minutes, set interval to 900.
If a shorter timeout has already been set for the login shell, that value will preempt any SSH setting made here. Keep in mind that some processes may stop SSH from correctly detecting that the user is idle.

RHEL-06-000231

CCI-000879

low

The SSH daemon must set a timeout count on idle sessions.

This ensures a user login will be terminated as soon as the `ClientAliveCountMax` is reached.

If , this is a finding.

To ensure the SSH idle timeout occurs precisely when the `ClientAliveCountMax` is set, edit `/etc/ssh/sshd_config` as follows:

    ClientAliveCountMax 0

RHEL-06-000234

CCI-000766

medium

The SSH daemon must ignore .rhosts files.

SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.

If , this is a finding.

SSH can emulate the behavior of the obsolete rsh command in allowing users to enable insecure access to their accounts via `.rhosts` files.
To ensure this behavior is disabled, add or correct the following line in `/etc/ssh/sshd_config`:

    IgnoreRhosts yes

RHEL-06-000235

CCI-000765

medium

The SSH daemon must not allow host-based authentication.

SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.

If , this is a finding.

SSH's cryptographic host-based authentication is more secure than `.rhosts` authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organization.
To disable host-based authentication, add or correct the following line in `/etc/ssh/sshd_config`:

    HostbasedAuthentication no

RHEL-06-000236

CCI-000766

medium

The SSH daemon must not allow host-based authentication.

SSH trust relationships mean a compromise on one host can allow an attacker to move trivially to other hosts.

If , this is a finding.

SSH's cryptographic host-based authentication is more secure than `.rhosts` authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organization.
To disable host-based authentication, add or correct the following line in `/etc/ssh/sshd_config`:

    HostbasedAuthentication no

RHEL-06-000237

CCI-000770

medium

The system must not permit root logins using remote access programs such as ssh.

Permitting direct root login reduces auditable information about who ran privileged commands on the system and also allows direct attack attempts on root's password.

If , this is a finding.

The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in `/etc/ssh/sshd_config`:

    PermitRootLogin no

RHEL-06-000239

CCI-000766

high

The SSH daemon must not allow authentication using an empty password.

Configuring this setting for the SSH daemon provides additional assurance that remote login via SSH will require a password, even in the event of misconfiguration elsewhere.

If , this is a finding.

To explicitly disallow remote login from accounts with empty passwords, add or correct the following line in `/etc/ssh/sshd_config`:

    PermitEmptyPasswords no

Any accounts with empty passwords should be disabled immediately, and PAM configuration should prevent users from being able to assign themselves empty passwords.

RHEL-06-000240

CCI-000048

medium

The SSH daemon must be configured with the Department of Defense (DoD) login banner.

The warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers. Alternatively, systems whose ownership should not be obvious should ensure usage of a banner that does not provide easy attribution.

If , this is a finding.

To enable the warning banner and ensure it is consistent across the system, add or correct the following line in `/etc/ssh/sshd_config`:

    Banner /etc/issue

Another section contains information on how to create an appropriate system-wide warning banner.

RHEL-06-000241

CCI-001414

low

The SSH daemon must not permit user environment settings.

SSH environment options potentially allow users to bypass access restriction in some configurations.

If , this is a finding.

To ensure users are not able to present environment options to the SSH daemon, add or correct the following line in `/etc/ssh/sshd_config`:

    PermitUserEnvironment no

RHEL-06-000243

CCI-001144

medium

The SSH daemon must be configured to use only FIPS 140-2 approved ciphers.

Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.

If , this is a finding.

Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in `/etc/ssh/sshd_config` demonstrates use of FIPS-approved ciphers:

    Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc

The man page `sshd_config(5)` contains a list of supported ciphers.

RHEL-06-000244

CCI-001145

medium

The operating system must employ FIPS-validated cryptography to protect unclassified information.

Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.

If , this is a finding.

Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in `/etc/ssh/sshd_config` demonstrates use of FIPS-approved ciphers:

    Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc

The man page `sshd_config(5)` contains a list of supported ciphers.

RHEL-06-000245

CCI-001146

medium

The operating system must employ NSA-approved cryptography to protect classified information.

Approved algorithms should impart some level of confidence in their implementation. These are also required for compliance.

If , this is a finding.

Limit the ciphers to those algorithms which are FIPS-approved. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in `/etc/ssh/sshd_config` demonstrates use of FIPS-approved ciphers:

    Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc,aes192-cbc,aes256-cbc

The man page `sshd_config(5)` contains a list of supported ciphers.

RHEL-06-000246

CCI-000366

low

The avahi service must be disabled.

Because the Avahi daemon service keeps an open network port, it is subject to network attacks. Its functionality is convenient but is only appropriate if the local network can be trusted.

If , this is a finding.

The `avahi-daemon` service can be disabled with the following command:

    $ sudo chkconfig avahi-daemon off

RHEL-06-000247

CCI-000160

medium

The system clock must be synchronized continuously, or at least daily.

Enabling the `ntpd` service ensures that the `ntpd` service will be running and that the system will synchronize its time to any servers specified. This is important whether the system is configured to be a client (and synchronize only its own clock) or it is also acting as an NTP server to other systems. Synchronizing time is essential for authentication services such as Kerberos, but it is also important for maintaining accurate logs and auditing possible security breaches.
The NTP daemon offers all of the functionality of `ntpdate`, which is now deprecated. Additional information on this is available at http://support.ntp.org/bin/view/Dev/DeprecatingNtpdate

If , this is a finding.

The `ntpd` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 ntpd on

RHEL-06-000248

CCI-000160

medium

The system clock must be synchronized to an authoritative DoD time source.

Synchronizing with an NTP server makes it possible to collate system logs from multiple sources or correlate computer events with real time events.

If , this is a finding.

To specify a remote NTP server for time synchronization, edit the file `/etc/ntp.conf`. Add or correct the following lines, substituting the IP or hostname of a remote NTP server for ntpserver:

    server ntpserver

This instructs the NTP software to contact that remote server to obtain time data.

RHEL-06-000249

CCI-000382

medium

Mail relaying must be restricted.

This ensures `postfix` accepts mail messages (such as cron job reports) from the local system only, and not from the network, which protects it from network attack.

If , this is a finding.

Edit the file `/etc/postfix/main.cf` to ensure that only the following `inet_interfaces` line appears:

    inet_interfaces = localhost

RHEL-06-000252

CCI-001453

medium

If the system is using LDAP for authentication or account information, the system must use a TLS connection using FIPS 140-2 approved cryptographic algorithms.

The ssl directive specifies whether to use ssl or not. If not specified it will default to no. It should be set to start_tls rather than doing LDAP over SSL.

If , this is a finding.

Configure LDAP to enforce TLS use. First, edit the file `/etc/pam_ldap.conf`, and add or correct the following lines:

    ssl start_tls

Then review the LDAP server and ensure TLS has been configured.

RHEL-06-000253

CCI-000776

medium

The LDAP client must use a TLS connection using trust certificates signed by the site CA.

The tls_cacertdir or tls_cacertfile directives are required when tls_checkpeer is configured (which is the default for openldap versions 2.1 and up). These directives define the path to the trust certificates signed by the site CA.

If , this is a finding.

Ensure a copy of a trusted CA certificate has been placed in the file `/etc/pki/tls/CA/cacert.pem`. Configure LDAP to enforce TLS use and to trust certificates signed by that CA. First, edit the file `/etc/pam_ldap.conf`, and add or correct either of the following lines:

    tls_cacertdir /etc/pki/tls/CA

or

    tls_cacertfile /etc/pki/tls/CA/cacert.pem

Then review the LDAP server and ensure TLS has been configured.

RHEL-06-000256

CCI-000366

low

The openldap-servers package must not be installed unless required.

The `openldap-servers` package is not installed by default on RHEL6 systems. It is needed only by the OpenLDAP server system, not clients which use LDAP for authentication. If the system is not intended for use as an LDAP server, `openldap-servers` should be removed.

If , this is a finding.

The `openldap-servers` package should be removed if not in use. Is this system the OpenLDAP server? If not, remove the package.

    $ sudo yum erase openldap-servers

The openldap-servers RPM is not installed by default on Red Hat Enterprise Linux 6 systems. It is needed only by the OpenLDAP server, not by the clients which use LDAP for authentication. If the system is not intended for use as an LDAP Server it should be removed.

RHEL-06-000257

CCI-000057

medium

The graphical desktop environment must set the idle timeout to no more than 15 minutes.

Setting the idle delay controls when the screensaver will start, and can be combined with screen locking to prevent access from passersby.

If , this is a finding.

Run the following command to set the idle time-out value for inactivity in the GNOME desktop to minutes:

    $ sudo gconftool-2 \
      --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type int \
      --set /desktop/gnome/session/idle_delay

RHEL-06-000258

CCI-000057

medium

The graphical desktop environment must automatically lock after 15 minutes of inactivity and the system must require user to re-authenticate to unlock the environment.

Enabling idle activation of the screensaver ensures the screensaver will be activated after the idle delay. Applications requiring continuous, real-time screen display (such as network management products) require the login session does not have administrator rights and the display station is located in a controlled-access area.

If , this is a finding.

Run the following command to activate the screensaver in the GNOME desktop after a period of inactivity:

    $ sudo gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /apps/gnome-screensaver/idle_activation_enabled true

RHEL-06-000259

CCI-000057

medium

The graphical desktop environment must have automatic lock enabled.

Enabling the activation of the screen lock after an idle period ensures password entry will be required in order to access the system, preventing access by passersby.

If , this is a finding.

Run the following command to activate locking of the screensaver in the GNOME desktop when it is activated:

    $ sudo gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /apps/gnome-screensaver/lock_enabled true

RHEL-06-000260

CCI-000060

low

The system must display a publicly-viewable pattern during a graphical desktop environment session lock.

Setting the screensaver mode to blank-only conceals the contents of the display from passersby.

If , this is a finding.

Run the following command to set the screensaver mode in the GNOME desktop to a blank screen:

    $ sudo gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /apps/gnome-screensaver/mode blank-only

RHEL-06-000261

CCI-000382

low

The Automatic Bug Reporting Tool (abrtd) service must not be running.

Mishandling crash data could expose sensitive information about vulnerabilities in software executing on the local system, as well as sensitive information from within a process's address space or registers.

If , this is a finding.

The Automatic Bug Reporting Tool (`abrtd`) daemon collects and reports crash data when an application crash is detected. Using a variety of plugins, abrtd can email crash reports to system administrators, log crash reports to files, or forward crash reports to a centralized issue tracking system such as RHTSupport. The `abrtd` service can be disabled with the following command:

    $ sudo chkconfig abrtd off

RHEL-06-000262

CCI-000382

low

The atd service must be disabled.

The `atd` service could be used by an unsophisticated insider to carry out activities outside of a normal login session, which could complicate accountability. Furthermore, the need to schedule tasks with `at` or `batch` is not common.

If , this is a finding.

The `at` and `batch` commands can be used to schedule tasks that are meant to be executed only once. This allows delayed execution in a manner similar to cron, except that it is not recurring. The daemon `atd` keeps track of tasks scheduled via `at` and `batch`, and executes them at the specified time. The `atd` service can be disabled with the following command:

    $ sudo chkconfig atd off

RHEL-06-000263

CCI-001250

low

Automated file system mounting tools must not be enabled unless needed.

Disabling the automounter permits the administrator to statically control filesystem mounting through `/etc/fstab`.

If , this is a finding.

The `autofs` daemon mounts and unmounts filesystems, such as user home directories shared via NFS, on demand. In addition, autofs can be used to handle removable media, and the default configuration provides the cdrom device as `/misc/cd`. However, this method of providing access to removable media is not common, so autofs can almost always be disabled if NFS is not in use. Even if NFS is required, it may be possible to configure filesystem mounts statically by editing `/etc/fstab` rather than relying on the automounter.
The `autofs` service can be disabled with the following command:

    $ sudo chkconfig autofs off

RHEL-06-000265

CCI-000382

low

The ntpdate service must not be running.

The `ntpdate` service may only be suitable for systems which are rebooted frequently enough that clock drift does not cause problems between reboots. In any event, the functionality of the ntpdate service is now available in the ntpd program and should be considered deprecated.

If , this is a finding.

The `ntpdate` service sets the local hardware clock by polling NTP servers when the system boots. It synchronizes to the NTP servers listed in `/etc/ntp/step-tickers` or `/etc/ntp.conf` and then sets the local hardware clock to the newly synchronized system time. The `ntpdate` service can be disabled with the following command:

    $ sudo chkconfig ntpdate off

RHEL-06-000266

CCI-000382

low

The oddjobd service must not be running.

The `oddjobd` service may provide necessary functionality in some environments, and can be disabled if it is not needed. Execution of tasks by privileged programs, on behalf of unprivileged ones, has traditionally been a source of privilege escalation security issues.

If , this is a finding.

The `oddjobd` service exists to provide an interface and access control mechanism through which specified privileged tasks can run tasks for unprivileged client applications. Communication with `oddjobd` through the system message bus. The `oddjobd` service can be disabled with the following command:

    $ sudo chkconfig oddjobd off

RHEL-06-000267

CCI-000382

low

The qpidd service must not be running.

The qpidd service is automatically installed when the "base" package selection is selected during installation. The qpidd service listens for network connections, which increases the attack surface of the system. If the system is not intended to receive AMQP traffic, then the `qpidd` service is not needed and should be disabled or removed.

If , this is a finding.

The `qpidd` service provides high speed, secure, guaranteed delivery services. It is an implementation of the Advanced Message Queuing Protocol. By default the qpidd service will bind to port 5672 and listen for connection attempts. The `qpidd` service can be disabled with the following command:

    $ sudo chkconfig qpidd off

RHEL-06-000268

CCI-000382

low

The rdisc service must not be running.

General-purpose systems typically have their network and routing information configured statically by a system administrator. Workstations or some special-purpose systems often use DHCP (instead of IRDP) to retrieve dynamic network configuration information.

If , this is a finding.

The `rdisc` service implements the client side of the ICMP Internet Router Discovery Protocol (IRDP), which allows discovery of routers on the local subnet. If a router is discovered then the local routing table is updated with a corresponding default route. By default this daemon is disabled. The `rdisc` service can be disabled with the following command:

    $ sudo chkconfig rdisc off

RHEL-06-000269 | CCI-000366 | medium | Remote file systems must be mounted with the nodev option. | Legitimate device files should only exist in the /dev directory. NFS mounts should not present device files to users. | If , this is a finding. | Add the `nodev` option to the fourth column of `/etc/fstab` for the line which controls mounting of any NFS mounts.

RHEL-06-000270

CCI-000366

medium

Remote file systems must be mounted with the nosuid option.

NFS mounts should not present suid binaries to users. Only vendor-supplied suid executables should be installed to their default location on the local filesystem.

If , this is a finding.

Add the `nosuid` option to the fourth column of `/etc/fstab` for the line which controls mounting of any NFS mounts.

RHEL-06-000271

CCI-000087

low

The noexec option must be added to removable media partitions.

Allowing users to execute binaries from removable media such as USB keys exposes the system to potential compromise.

If , this is a finding.

The `noexec` mount option prevents the direct execution of binaries on the mounted filesystem. Preventing the direct execution of binaries from removable media (such as a USB key) provides a defense against malicious software that may be present on such untrusted media. Add the `noexec` option to the fourth column of `/etc/fstab` for the line which controls mounting of any removable media partitions.

RHEL-06-000272

CCI-000366

low

The system must use SMB client signing for connecting to samba servers using smbclient.

Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit.

If , this is a finding.

To require samba clients running `smbclient` to use packet signing, add the following to the `[global]` section of the Samba configuration file, `/etc/samba/smb.conf`:

    client signing = mandatory

Requiring samba clients such as `smbclient` to use packet signing ensures they can only communicate with servers that support packet signing.

RHEL-06-000273

CCI-000366

low

The system must use SMB client signing for connecting to samba servers using mount.cifs.

Packet signing can prevent man-in-the-middle attacks which modify SMB packets in transit.

If , this is a finding.

Require packet signing of clients who mount Samba shares using the `mount.cifs` program (e.g., those who specify shares in `/etc/fstab`). To do so, ensure signing options (either `sec=krb5i` or `sec=ntlmv2i`) are used.
See the `mount.cifs(8)` man page for more information. A Samba client should only communicate with servers who can support SMB packet signing.

RHEL-06-000274

CCI-000200

medium

The system must prohibit the reuse of passwords within twenty-four iterations.

Preventing re-use of previous passwords helps ensure that a compromised password is not re-used by a user.

If , this is a finding.

Do not allow users to reuse recent passwords. This can be accomplished by using the `remember` option for the `pam_unix` or `pam_pwhistory` PAM modules. In the file `/etc/pam.d/system-auth`, append `remember=` to the line which refers to the `pam_unix.so` or `pam_pwhistory.so`module, as shown below:

- for the `pam_unix.so` case:

      password sufficient pam_unix.so existing_options remember=

- for the `pam_pwhistory.so` case:

      password requisite pam_pwhistory.so existing_options remember=

The DoD STIG requirement is 5 passwords.

RHEL-06-000275

CCI-001019

low

The operating system must employ cryptographic mechanisms to protect information in storage.

The risk of a system's physical compromise, particularly mobile systems such as laptops, places its data at risk of compromise. Encrypting this data mitigates the risk of its loss if the system is lost.

If , this is a finding.

Red Hat Enterprise Linux 6 natively supports partition encryption through the Linux Unified Key Setup-on-disk-format (LUKS) technology. The easiest way to encrypt a partition is during installation time.
For manual installations, select the `Encrypt` checkbox during partition creation to encrypt the partition. When this option is selected the system will prompt for a passphrase to use in decrypting the partition. The passphrase will subsequently need to be entered manually every time the system boots.
For automated/unattended installations, it is possible to use Kickstart by adding the `--encrypted` and `--passphrase=` options to the definition of each partition to be encrypted. For example, the following line would encrypt the root partition:

    part / --fstype=ext3 --size=100 --onpart=hda1 --encrypted --passphrase=PASSPHRASE

Any PASSPHRASE is stored in the Kickstart in plaintext, and the Kickstart must then be protected accordingly. Omitting the `--passphrase=` option from the partition definition will cause the installer to pause and interactively ask for the passphrase during installation.
By default, the `Anaconda` installer uses `aes-xts-plain64` cipher with a minimum `512` bit key size which should be compatible with FIPS enabled.
Detailed information on encrypting partitions using LUKS or LUKS ciphers can be found on the Red Hat Documentation web site:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/chap-Security_Guide-Encryption.html#sect-Security_Guide-LUKS_Disk_Encryption

RHEL-06-000276

CCI-001199

low

The operating system must protect the confidentiality and integrity of data at rest.

The risk of a system's physical compromise, particularly mobile systems such as laptops, places its data at risk of compromise. Encrypting this data mitigates the risk of its loss if the system is lost.

If , this is a finding.

Red Hat Enterprise Linux 6 natively supports partition encryption through the Linux Unified Key Setup-on-disk-format (LUKS) technology. The easiest way to encrypt a partition is during installation time.
For manual installations, select the `Encrypt` checkbox during partition creation to encrypt the partition. When this option is selected the system will prompt for a passphrase to use in decrypting the partition. The passphrase will subsequently need to be entered manually every time the system boots.
For automated/unattended installations, it is possible to use Kickstart by adding the `--encrypted` and `--passphrase=` options to the definition of each partition to be encrypted. For example, the following line would encrypt the root partition:

    part / --fstype=ext3 --size=100 --onpart=hda1 --encrypted --passphrase=PASSPHRASE

Any PASSPHRASE is stored in the Kickstart in plaintext, and the Kickstart must then be protected accordingly. Omitting the `--passphrase=` option from the partition definition will cause the installer to pause and interactively ask for the passphrase during installation.
By default, the `Anaconda` installer uses `aes-xts-plain64` cipher with a minimum `512` bit key size which should be compatible with FIPS enabled.
Detailed information on encrypting partitions using LUKS or LUKS ciphers can be found on the Red Hat Documentation web site:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/chap-Security_Guide-Encryption.html#sect-Security_Guide-LUKS_Disk_Encryption

RHEL-06-000277

CCI-001200

low

The operating system must employ cryptographic mechanisms to prevent unauthorized disclosure of data at rest unless otherwise protected by alternative physical measures.

The risk of a system's physical compromise, particularly mobile systems such as laptops, places its data at risk of compromise. Encrypting this data mitigates the risk of its loss if the system is lost.

If , this is a finding.

Red Hat Enterprise Linux 6 natively supports partition encryption through the Linux Unified Key Setup-on-disk-format (LUKS) technology. The easiest way to encrypt a partition is during installation time.
For manual installations, select the `Encrypt` checkbox during partition creation to encrypt the partition. When this option is selected the system will prompt for a passphrase to use in decrypting the partition. The passphrase will subsequently need to be entered manually every time the system boots.
For automated/unattended installations, it is possible to use Kickstart by adding the `--encrypted` and `--passphrase=` options to the definition of each partition to be encrypted. For example, the following line would encrypt the root partition:

    part / --fstype=ext3 --size=100 --onpart=hda1 --encrypted --passphrase=PASSPHRASE

Any PASSPHRASE is stored in the Kickstart in plaintext, and the Kickstart must then be protected accordingly. Omitting the `--passphrase=` option from the partition definition will cause the installer to pause and interactively ask for the passphrase during installation.
By default, the `Anaconda` installer uses `aes-xts-plain64` cipher with a minimum `512` bit key size which should be compatible with FIPS enabled.
Detailed information on encrypting partitions using LUKS or LUKS ciphers can be found on the Red Hat Documentation web site:
https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Security_Guide/chap-Security_Guide-Encryption.html#sect-Security_Guide-LUKS_Disk_Encryption

RHEL-06-000282

CCI-000366

medium

There must be no world-writable files on the system.

Data in world-writable files can be modified by any user on the system. In almost all circumstances, files can be configured using a combination of user and group permissions to support whatever legitimate access is needed without the risk caused by world-writable files.

If , this is a finding.

It is generally a good idea to remove global (other) write access to a file when it is discovered. However, check with documentation for specific applications before making changes. Also, monitor for recurring world-writable files, as these may be symptoms of a misconfigured application or user account. Finally, this applies to real files and not virtual files that are a part of pseudo file systems such as `sysfs` or `procfs`.

RHEL-06-000284

CCI-001668

high

The system must use and update a DoD-approved virus scan program.

Virus scanning software can be used to detect if a system has been compromised by computer viruses, as well as to limit their spread to other systems.

If , this is a finding.

Install virus scanning software, which uses signatures to search for the presence of viruses on the filesystem. The McAfee VirusScan Enterprise for Linux virus scanning tool is provided for DoD systems. Ensure virus definition files are no older than 7 days, or their last release. Configure the virus scanning software to perform scans dynamically on all accessed files. If this is not possible, configure the system to scan all altered files on the system on a daily basis. If the system processes inbound SMTP mail, configure the virus scanner to scan all received mail.

RHEL-06-000285

CCI-001263

medium

The system must have a host-based intrusion detection tool installed.

Host-based intrusion detection tools provide a system-level defense when an intruder gains access to a system or network.

If , this is a finding.

The base Red Hat platform already includes a sophisticated auditing system that can detect intruder activity, as well as SELinux, which provides host-based intrusion prevention capabilities by confining privileged programs and user sessions which may become compromised.
In DoD environments, supplemental intrusion detection tools, such as, the McAfee Host-based Security System, are available to integrate with existing infrastructure. When these supplemental tools interfere with the proper functioning of SELinux, SELinux takes precedence.

RHEL-06-000286

CCI-000366

high

The x86 Ctrl-Alt-Delete key sequence must be disabled.

A locally logged-in user who presses Ctrl-Alt-Del, when at the console, can reboot the system. If accidentally pressed, as could happen in the case of mixed OS environment, this can create the risk of short-term loss of availability of systems due to unintentional reboot. In the GNOME graphical environment, risk of unintentional reboot from the Ctrl-Alt-Del sequence is reduced because the user will be prompted before any action is taken. NOTE: When updating the `initscripts` package on a Red Hat Enterprise Linux 6 system, custom changes to `/etc/init/control-alt-delete.conf` may be overwritten. Refer to https://access.redhat.com/site/solutions/70464 for additional information.

If , this is a finding.

By default, the system includes the following line in `/etc/init/control-alt-delete.conf` to reboot the system when the Ctrl-Alt-Del key sequence is pressed:

    exec /sbin/shutdown -r now "Control-Alt-Delete pressed"

To configure the system to log a message instead of rebooting the system, alter that line to read as follows:

    exec /usr/bin/logger -p security.info "Control-Alt-Delete pressed"

RHEL-06-000287

CCI-000366

low

The postfix service must be enabled for mail delivery.

Local mail delivery is essential to some system maintenance and notification tasks.

If , this is a finding.

The Postfix mail transfer agent is used for local mail delivery within the system. The default configuration only listens for connections to the default SMTP port (port 25) on the loopback interface (127.0.0.1). It is recommended to leave this service enabled for local mail delivery. The `postfix` service can be enabled with the following command:

    $ sudo chkconfig --level 2345 postfix on

RHEL-06-000288

CCI-000366

medium

The sendmail package must be removed.

The sendmail software was not developed with security in mind and its design prevents it from being effectively contained by SELinux. Postfix should be used instead.

If , this is a finding.

Sendmail is not the default mail transfer agent and is not installed by default. The `sendmail` package can be removed with the following command:

    $ sudo yum erase sendmail

RHEL-06-000289

CCI-000382

low

The netconsole service must be disabled unless required.

The `netconsole` service is not necessary unless there is a need to debug kernel panics, which is not common.

If , this is a finding.

The `netconsole` service is responsible for loading the netconsole kernel module, which logs kernel printk messages over UDP to a syslog server. This allows debugging of problems where disk logging fails and serial consoles are impractical. The `netconsole` service can be disabled with the following command:

    $ sudo chkconfig netconsole off

RHEL-06-000290

CCI-001436

medium

X Windows must not be enabled unless required.

Unnecessary services should be disabled to decrease the attack surface of the system.

If , this is a finding.

Setting the system's runlevel to 3 will prevent automatic startup of the X server. To do so, ensure the following line in `/etc/inittab` features a `3` as shown:

    id:3:initdefault:

RHEL-06-000291

CCI-NaN

low

The xorg-x11-server-common (X Windows) package must not be installed, unless required.

Unnecessary packages should not be installed to decrease the attack surface of the system.

If , this is a finding.

Removing all packages which constitute the X Window System ensures users or malicious software cannot start X. To do so, run the following command:

    $ sudo yum groupremove "X Window System"

RHEL-06-000292

CCI-000366

medium

The DHCP client must be disabled if not needed.

DHCP relies on trusting the local network. If the local network is not trusted, then it should not be used. However, the automatic configuration provided by DHCP is commonly used and the alternative, manual configuration, presents an unacceptable burden in many circumstances.

If , this is a finding.

For each interface on the system (e.g. eth0), edit `/etc/sysconfig/network-scripts/ifcfg-interface` and make the following changes:

- Correct the BOOTPROTO line to read:

      BOOTPROTO=none

- Add or correct the following lines, substituting the appropriate values based on your site's addressing scheme:

      NETMASK=255.255.255.0
      IPADDR=192.168.1.2
      GATEWAY=192.168.1.1

RHEL-06-000294 | CCI-000366 | low | All GIDs referenced in /etc/passwd must be defined in /etc/group | Inconsistency in GIDs between `/etc/passwd` and `/etc/group` could lead to a user having unintended rights. | If , this is a finding. | Add a group to the system for each GID referenced without a corresponding group.
RHEL-06-000296 | CCI-000804 | low | All accounts on the system must have unique user or account names | Unique usernames allow for accountability on the system. | If , this is a finding. | Change usernames, or delete accounts, so each has a unique name.

RHEL-06-000299

CCI-000366

low

The system must require passwords to contain no more than three consecutive repeating characters.

Passwords with excessive repeating characters may be more vulnerable to password-guessing attacks.

If , this is a finding.

The pam_cracklib module's `maxrepeat` parameter controls requirements for consecutive repeating characters. When set to a positive number, it will reject passwords which contain more than that number of consecutive characters. Add `maxrepeat=` after pam_cracklib.so to prevent a run of ( + 1) or more identical characters:

    password required pam_cracklib.so maxrepeat=

RHEL-06-000300

CCI-000224

low

All files and directories must have a valid owner.

Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.

If , this is a finding.

If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user.

RHEL-06-000301

CCI-000224

low

All files must be owned by a group.

Unowned files do not directly imply a security problem, but they are generally a sign that something is amiss. They may be caused by an intruder, by incorrect software installation or draft software removal, or by failure to remove all files belonging to a deleted account. The files should be repaired so they will not cause problems when accounts are created in the future, and the cause should be discovered and addressed.

If , this is a finding.

If any files are not owned by a group, then the cause of their lack of group-ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate group.

RHEL-06-000302

CCI-000374

medium

A file integrity tool must be used at least weekly to check for unauthorized file changes, particularly the addition of unauthorized system libraries or binaries, or for unauthorized modification to authorized system libraries or binaries.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000303

CCI-000416

medium

The operating system must employ automated mechanisms, per organization defined frequency, to detect the addition of unauthorized components/devices into the operating system.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000304

CCI-001069

medium

The operating system must employ automated mechanisms to detect the presence of unauthorized software on organizational information systems and notify designated organizational officials in accordance with the organization defined frequency.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000305

CCI-001263

medium

The operating system must provide a near real-time alert when any of the organization defined list of compromise or potential compromise indicators occurs.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000306

CCI-001297

medium

The operating system must detect unauthorized changes to software and information.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000307

CCI-001589

medium

The operating system must ensure unauthorized, security-relevant configuration changes detected are tracked.

By default, AIDE does not install itself for periodic execution. Periodically running AIDE is necessary to reveal unexpected changes in installed files.

If , this is a finding.

To implement a daily execution of AIDE at 4:05am using cron, add the following line to `/etc/crontab`:

    05 4 * * * root /usr/sbin/aide --check

AIDE can be executed periodically through other means; this is merely one example.

RHEL-06-000308

CCI-000366

low

Process core dumps must be disabled unless needed.

A core dump includes a memory image taken at the time the operating system terminates an application. The memory image could contain sensitive data and is generally useful only for developers trying to debug problems.

If , this is a finding.

To disable core dumps for all users, add the following line to `/etc/security/limits.conf`:

    *     hard   core    0

RHEL-06-000309

CCI-000764

high

The NFS server must not have the insecure file locking option enabled.

Allowing insecure file locking could allow for sensitive data to be viewed or edited by an unauthorized user.

If , this is a finding.

By default the NFS server requires secure file-lock requests, which require credentials from the client in order to lock a file. Most NFS clients send credentials with file lock requests, however, there are a few clients that do not send credentials when requesting a file-lock, allowing the client to only be able to lock world-readable files. To get around this, the `insecure_locks` option can be used so these clients can access the desired export. This poses a security risk by potentially allowing the client access to data for which it does not have authorization. Remove any instances of the `insecure_locks` option from the file `/etc/exports`.

RHEL-06-000311

CCI-000143

medium

The audit system must provide a warning when allocated audit record storage volume reaches a documented percentage of maximum audit record storage capacity.

Notifying administrators of an impending disk space problem may allow them to take corrective action prior to any disruption.

If , this is a finding.

The `auditd` service can be configured to take an action when disk space starts to run low. Edit the file `/etc/audit/auditd.conf`. Modify the following line, substituting ACTION appropriately:

    space_left_action = ACTION

Possible values for ACTION are described in the `auditd.conf` man page. These include:

- `ignore`
- `syslog`
- `email`
- `exec`
- `suspend`
- `single`
- `halt`

Set this to `email` (instead of the default, which is `suspend`) as it is more likely to get prompt attention. Acceptable values also include `suspend`, `single`, and `halt`.

RHEL-06-000313

CCI-000139

medium

The audit system must identify staff members to receive notifications of audit log storage volume capacity issues.

Email sent to the root account is typically aliased to the administrators of the system, who can take appropriate action.

If , this is a finding.

The `auditd` service can be configured to send email to a designated account in certain situations. Add or correct the following line in `/etc/audit/auditd.conf` to ensure that administrators are notified via email for those situations:

    action_mail_acct =

RHEL-06-000315

CCI-000085

medium

The Bluetooth kernel module must be disabled.

If Bluetooth functionality must be disabled, preventing the kernel from loading the kernel module provides an additional safeguard against its activation.

If , this is a finding.

The kernel's module loading system can be configured to prevent loading of the Bluetooth module. Add the following to the appropriate `/etc/modprobe.d` configuration file to prevent the loading of the Bluetooth module:

    install bluetooth /bin/true

RHEL-06-000317

CCI-001250

medium

The system must have USB Mass Storage disabled unless needed.

USB storage devices such as thumb drives can be used to introduce malicious software.

If , this is a finding.

To prevent USB storage devices from being used, configure the kernel module loading system to prevent automatic loading of the USB storage driver. To configure the system to prevent the `usb-storage` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install usb-storage /bin/true

This will prevent the `modprobe` program from loading the `usb-storage` module, but will not prevent an administrator (or another program) from using the `insmod` program to load the module manually.

RHEL-06-000319

CCI-000054

low

The system must limit users to 10 simultaneous system logins, or a site-defined number, in accordance with operational requirements.

Limiting simultaneous user logins can insulate the system from denial of service problems caused by excessive logins. Automated login processes operating improperly or maliciously may result in an exceptional number of simultaneous login sessions.

If , this is a finding.

Limiting the number of allowed users and sessions per user can limit risks related to Denial of Service attacks. This addresses concurrent sessions for a single account and does not address concurrent sessions by a single user via multiple accounts. The DoD requirement is 10. To set the number of concurrent sessions per user add the following line in `/etc/security/limits.conf`:

    * hard maxlogins

RHEL-06-000320

CCI-001109

medium

The systems local firewall must implement a deny-all, allow-by-exception policy for forwarded packets.

In `iptables`, the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

If , this is a finding.

To set the default policy to DROP (instead of ACCEPT) for the built-in FORWARD chain which processes packets that will be forwarded from one interface to another, add or correct the following line in `/etc/sysconfig/iptables`:

    :FORWARD DROP [0:0]

RHEL-06-000321

CCI-001130

low

The system must provide VPN connectivity for communications over untrusted networks.

Providing the ability for remote users or systems to initiate a secure VPN connection protects information when it is transmitted over a wide area network.

If , this is a finding.

The openswan and libreswan packages provide an implementation of IPsec and IKE, which permits the creation of secure tunnels over untrusted networks. The `openswan` package can be installed with the following command:

    $ sudo yum install openswan

The `libreswan` package can be installed with the following command:

    $ sudo yum install libreswan

RHEL-06-000324

CCI-000050

medium

A login banner must be displayed immediately prior to, or as part of, graphical desktop environment login prompts.

An appropriate warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers.

If , this is a finding.

To enable displaying a login warning banner in the GNOME Display Manager's login screen, run the following command:

    $ sudo gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type bool \
      --set /apps/gdm/simple-greeter/banner_message_enable true

To display a banner, this setting must be enabled and then banner text must also be set.

RHEL-06-000326

CCI-NaN

medium

The Department of Defense (DoD) login banner must be displayed immediately prior to, or as part of, graphical desktop environment login prompts.

An appropriate warning message reinforces policy awareness during the login process and facilitates possible legal action against attackers.

If , this is a finding.

To set the text shown by the GNOME Display Manager in the login screen, run the following command:

    $ sudo gconftool-2 --direct \
      --config-source xml:readwrite:/etc/gconf/gconf.xml.mandatory \
      --type string \
      --set /apps/gdm/simple-greeter/banner_message_text \
      "Text of the warning banner here"

When entering a warning banner that spans several lines, remember to begin and end the string with `"`. This command writes directly either to the `/etc/gconf/gconf.xml.mandatory/%gconf-tree.xml` if it exists or to the file `/etc/gconf/gconf.xml.mandatory/apps/gdm/simple-greeter/%gconf.xml`. Either of these files can later be edited directly if necessary.

RHEL-06-000331

CCI-000085

medium

The Bluetooth service must be disabled.

Disabling the `bluetooth` service prevents the system from attempting connections to Bluetooth devices, which entails some security risk. Nevertheless, variation in this risk decision may be expected due to the utility of Bluetooth connectivity and its limited range.

If , this is a finding.

The `bluetooth` service can be disabled with the following command:

    $ sudo chkconfig bluetooth off

    $ sudo service bluetooth stop

RHEL-06-000334

CCI-000017

low

Accounts must be locked upon 35 days of inactivity.

Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials.

If , this is a finding.

To specify the number of days after a password expires (which signifies inactivity) until an account is permanently disabled, add or correct the following lines in `/etc/default/useradd`, substituting `NUM_DAYS` appropriately:

    INACTIVE=

A value of 35 is recommended. If a password is currently on the verge of expiration, then 35 days remain until the account is automatically disabled. However, if the password will not expire for another 60 days, then 95 days could elapse until the account would be automatically disabled. See the `useradd` man page for more information. Determining the inactivity timeout must be done with careful consideration of the length of a "normal" period of inactivity for users in the particular environment. Setting the timeout too low incurs support costs and also has the potential to impact availability of the system to legitimate users.

RHEL-06-000335

CCI-000795

low

The operating system must manage information system identifiers for users and devices by disabling the user identifier after an organization defined time period of inactivity.

Disabling inactive accounts ensures that accounts which may not have been responsibly removed are not available to attackers who may have compromised their credentials.

If , this is a finding.

To specify the number of days after a password expires (which signifies inactivity) until an account is permanently disabled, add or correct the following lines in `/etc/default/useradd`, substituting `NUM_DAYS` appropriately:

    INACTIVE=

A value of 35 is recommended. If a password is currently on the verge of expiration, then 35 days remain until the account is automatically disabled. However, if the password will not expire for another 60 days, then 95 days could elapse until the account would be automatically disabled. See the `useradd` man page for more information. Determining the inactivity timeout must be done with careful consideration of the length of a "normal" period of inactivity for users in the particular environment. Setting the timeout too low incurs support costs and also has the potential to impact availability of the system to legitimate users.

RHEL-06-000336

CCI-000366

low

The sticky bit must be set on all public directories.

Failing to set the sticky bit on public directories allows unauthorized users to delete files in the directory structure.
The only authorized public directories are those temporary directories supplied with the system, or those designed to be temporary file repositories. The setting is normally reserved for directories used by the system, by users for temporary file storage (such as `/tmp`), and for directories requiring global read/write access.

If , this is a finding.

When the so-called 'sticky bit' is set on a directory, only the owner of a given file may remove that file from the directory. Without the sticky bit, any user with write access to a directory may remove any file in the directory. Setting the sticky bit prevents users from removing each other's files. In cases where there is no reason for a directory to be world-writable, a better solution is to remove that permission rather than to set the sticky bit. However, if a directory is used by a particular application, consult that application's documentation instead of blindly changing modes.
To set the sticky bit on a world-writable directory DIR, run the following command:

    $ sudo chmod +t DIR

RHEL-06-000337

CCI-000366

low

All public directories must be owned by a system account.

Allowing a user account to own a world-writable directory is undesirable because it allows the owner of that directory to remove or replace any files that may be placed in the directory by other users.

If , this is a finding.

All directories in local partitions which are world-writable should be owned by root or another system account. If any world-writable directories are not owned by a system account, this should be investigated. Following this, the files should be deleted or assigned to an appropriate group.

RHEL-06-000338

CCI-000366

high

The TFTP daemon must operate in secure mode which provides access only to a single directory on the host file system.

Using the `-s` option causes the TFTP service to only serve files from the given directory. Serving files from an intentionally-specified directory reduces the risk of sharing files which should remain private.

If , this is a finding.

If running the `tftp` service is necessary, it should be configured to change its root directory at startup. To do so, ensure `/etc/xinetd.d/tftp` includes `-s` as a command line argument, as shown in the following example (which is also the default):

    server_args = -s /var/lib/tftpboot

RHEL-06-000339

CCI-000130

low

The FTP daemon must be configured for logging or verbose mode.

To trace malicious activity facilitated by the FTP service, it must be configured to ensure that all commands sent to the FTP server are logged using the verbose vsftpd log format. The default vsftpd log file is `/var/log/vsftpd.log`.

If , this is a finding.

Add or correct the following configuration options within the `vsftpd` configuration file, located at `/etc/vsftpd/vsftpd.conf`:

    xferlog_enable=YES
    xferlog_std_format=NO
    log_ftp_protocol=YES

RHEL-06-000340

CCI-000366

medium

The snmpd service must use only SNMP protocol version 3 or newer.

Earlier versions of SNMP are considered insecure, as they potentially allow unauthorized access to detailed system management information.

If , this is a finding.

Edit `/etc/snmp/snmpd.conf`, removing any references to `rocommunity`, `rwcommunity`, or `com2sec`. Upon doing that, restart the SNMP service:

    $ sudo service snmpd restart

RHEL-06-000341

CCI-000366

high

The snmpd service must not use a default password.

Presence of the default SNMP password enables querying of different system aspects and could result in unauthorized knowledge of the system.

If , this is a finding.

Edit `/etc/snmp/snmpd.conf`, remove default community string `public`. Upon doing that, restart the SNMP service:

    $ sudo service snmpd restart

RHEL-06-000342

CCI-000366

low

The system default umask for the bash shell must be 077.

The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.

If , this is a finding.

To ensure the default umask for users of the Bash shell is set properly, add or correct the `umask` setting in `/etc/bashrc` to read as follows:

    umask

RHEL-06-000343

CCI-000366

low

The system default umask for the csh shell must be 077.

The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.

If , this is a finding.

To ensure the default umask for users of the C shell is set properly, add or correct the `umask` setting in `/etc/csh.cshrc` to read as follows:

    umask

RHEL-06-000344

CCI-000366

low

The system default umask in /etc/profile must be 077.

The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read or written to by unauthorized users.

If , this is a finding.

To ensure the default umask controlled by `/etc/profile` is set properly, add or correct the `umask` setting in `/etc/profile` to read as follows:

    umask

RHEL-06-000345

CCI-000366

low

The system default umask in /etc/login.defs must be 077.

The umask value influences the permissions assigned to files when they are created. A misconfigured umask value could result in files with excessive permissions that can be read and written to by unauthorized users.

If , this is a finding.

To ensure the default umask controlled by `/etc/login.defs` is set properly, add or correct the `UMASK` setting in `/etc/login.defs` to read as follows:

    UMASK

RHEL-06-000346

CCI-000366

low

The system default umask for daemons must be 027 or 022.

The umask influences the permissions assigned to files created by a process at run time. An unnecessarily permissive umask could result in files being created with insecure permissions.

If , this is a finding.

The file `/etc/init.d/functions` includes initialization parameters for most or all daemons started at boot time. The default umask of 022 prevents creation of group- or world-writable files. To set the default umask for daemons, edit the following line, inserting 022 or 027 for umask appropriately:

    umask

Setting the umask to too restrictive a setting can cause serious errors at runtime. Many daemons on the system already individually restrict themselves to a umask of 077 in their own init scripts.

RHEL-06-000347

CCI-000196

medium

There must be no .netrc files on the system.

Unencrypted passwords for remote FTP servers may be stored in `.netrc` files. DoD policy requires passwords be encrypted in storage and not used in access scripts.

If , this is a finding.

The `.netrc` files contain login information used to auto-login into FTP servers and reside in the user's home directory. These files may contain unencrypted passwords to remote FTP servers making them susceptible to access by unauthorized users and should not be used. Any `.netrc` files should be removed.

RHEL-06-000348

CCI-000048

medium

The FTPS/FTP service on the system must be configured with the Department of Defense (DoD) login banner.

This setting will cause the system greeting banner to be used for FTP connections as well.

If , this is a finding.

Edit the vsftpd configuration file, which resides at `/etc/vsftpd/vsftpd.conf` by default. Add or correct the following configuration options:

    banner_file=/etc/issue

RHEL-06-000349

CCI-000765

medium

The system must be configured to require the use of a CAC, PIV compliant hardware token, or Alternate Logon Token (ALT) for authentication.

Smart card login provides two-factor authentication stronger than that provided by a username and password combination. Smart cards leverage PKI (public key infrastructure) in order to provide and verify credentials.

If , this is a finding.

To enable smart card authentication, consult the documentation at:

- https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Managing_Smart_Cards/enabling-smart-card-login.html

For guidance on enabling SSH to authenticate against a Common Access Card (CAC), consult documentation at:

- https://access.redhat.com/solutions/82273

RHEL-06-000356

CCI-000047

medium

The system must require administrator action to unlock an account locked by excessive failed login attempts.

Locking out user accounts after a number of incorrect attempts prevents direct password guessing attacks. Ensuring that an administrator is involved in unlocking locked accounts draws appropriate attention to such situations.

If , this is a finding.

To configure the system to lock out accounts after a number of incorrect login attempts and require an administrator to unlock the account using `pam_faillock.so`, modify the content of both `/etc/pam.d/system-auth` and `/etc/pam.d/password-auth` as follows:

- Add the following line immediately `before` the `pam_unix.so` statement in the `AUTH` section:

      auth required pam_faillock.so preauth silent deny= unlock_time= fail_interval=

- Add the following line immediately `after` the `pam_unix.so` statement in the `AUTH` section:

      auth [default=die] pam_faillock.so authfail deny= unlock_time= fail_interval=

- Add the following line immediately `before` the `pam_unix.so` statement in the `ACCOUNT` section:

      account required pam_faillock.so

RHEL-06-000357

CCI-001452

medium

The system must disable accounts after excessive login failures within a 15-minute interval.

Locking out user accounts after a number of incorrect attempts within a specific period of time prevents direct password guessing attacks.

If , this is a finding.

Utilizing `pam_faillock.so`, the `fail_interval` directive configures the system to lock out accounts after a number of incorrect login attempts. Modify the content of both `/etc/pam.d/system-auth` and `/etc/pam.d/password-auth` as follows:

- Add the following line immediately `before` the `pam_unix.so` statement in the `AUTH` section:

      auth required pam_faillock.so preauth silent deny= unlock_time= fail_interval=

- Add the following line immediately `after` the `pam_unix.so` statement in the `AUTH` section:

      auth [default=die] pam_faillock.so authfail deny= unlock_time= fail_interval=

- Add the following line immediately `before` the `pam_unix.so` statement in the `ACCOUNT` section:

      account required pam_faillock.so

RHEL-06-000372

CCI-000366

medium

The operating system, upon successful logon/access, must display to the user the number of unsuccessful logon/access attempts since the last successful logon/access.

Users need to be aware of activity that occurs regarding their account. Providing users with information regarding the number of unsuccessful attempts that were made to login to their account allows the user to determine if any unauthorized activity has occurred and gives them an opportunity to notify administrators.

If , this is a finding.

To configure the system to notify users of last login/access using `pam_lastlog`, add the following line immediately after `session required pam_limits.so`:

    session       required     pam_lastlog.so showfailed

RHEL-06-000383

CCI-000163

medium

Audit log files must have mode 0640 or less permissive.

If users can write to audit logs, audit trails can be modified or destroyed.

If , this is a finding.

If `log_group` in `/etc/audit/auditd.conf` is set to a group other than the `root` group account, change the mode of the audit log files with the following command:

    $ sudo chmod 0640 audit_file

Otherwise, change the mode of the audit log files with the following command:

    $ sudo chmod 0600 audit_file

RHEL-06-000384

CCI-000162

medium

Audit log files must be owned by root.

Failure to give ownership of the audit log files to root allows the designated owner, and unauthorized users, potential access to sensitive information.

If , this is a finding.

To properly set the owner of `/var/log`, run the command:

    $ sudo chown root /var/log

RHEL-06-000503

CCI-NaN

medium

The operating system must enforce requirements for the connection of mobile devices to operating systems.

USB storage devices such as thumb drives can be used to introduce malicious software.

If , this is a finding.

To prevent USB storage devices from being used, configure the kernel module loading system to prevent automatic loading of the USB storage driver. To configure the system to prevent the `usb-storage` kernel module from being loaded, add the following line to a file in the directory `/etc/modprobe.d`:

    install usb-storage /bin/true

This will prevent the `modprobe` program from loading the `usb-storage` module, but will not prevent an administrator (or another program) from using the `insmod` program to load the module manually.

RHEL-06-000509

CCI-000136

low

The system must forward audit records to the syslog service.

The auditd service does not include the ability to send audit records to a centralized server for management directly. It does, however, include a plug-in for audit event multiplexor (audispd) to pass audit records to the local syslog server

If , this is a finding.

To configure the `auditd` service to use the `syslog` plug-in of the `audispd` audit event multiplexor, set the `active` line in `/etc/audisp/plugins.d/syslog.conf` to `yes`. Restart the `auditd` service:

    $ sudo service auditd restart

RHEL-06-000518

CCI-000366

low

The system package management tool must verify permissions on all files and directories associated with packages.

Permissions on system binaries and configuration files that are too generous could allow an unauthorized user to gain privileges that they should not have. The permissions set by the vendor should be maintained. Any deviations from this baseline should be investigated.

If , this is a finding.

The RPM package management system can check file access permissions of installed software packages, including many that are important to system security. After locating a file with incorrect permissions which can be found with

    $ rpm -Va | grep '^.M'

, run the following command to determine which package owns it:

    $ rpm -qf FILENAME

Next, run the following command to reset its permissions to the correct values:

    $ sudo rpm --setperms PACKAGENAME

RHEL-06-000519

CCI-000366

low

The system package management tool must verify contents of all files associated with packages.

The hashes of important files like system executables should match the information given by the RPM database. Executables with erroneous hashes could be a sign of nefarious activity on the system.

If , this is a finding.

The RPM package management system can check the hashes of installed software packages, including many that are important to system security. Run the following command to list which files on the system have hashes that differ from what is expected by the RPM database:

    $ rpm -Va | grep '^..5'

A "c" in the second column indicates that a file is a configuration file, which may appropriately be expected to change. If the file was not expected to change, investigate the cause of the change using audit logs or other means. The package can then be reinstalled to restore the file. Run the following command to determine which package owns the file:

    $ rpm -qf FILENAME

The package can be reinstalled from a yum repository using the command:

    $ sudo yum reinstall PACKAGENAME

Alternatively, the package can be reinstalled from trusted media using the command:

    $ sudo rpm -Uvh PACKAGENAME

RHEL-06-000523

CCI-000066

medium

The systems local IPv6 firewall must implement a deny-all, allow-by-exception policy for inbound packets.

In `ip6tables`, the default policy is applied only after all the applicable rules in the table are examined for a match. Setting the default policy to `DROP` implements proper design for a firewall, i.e. any packets which are not explicitly permitted should not be accepted.

If , this is a finding.

To set the default policy to DROP (instead of ACCEPT) for the built-in INPUT chain which processes incoming packets, add or correct the following line in `/etc/sysconfig/ip6tables`:

    :INPUT DROP [0:0]

If changes were required, reload the ip6tables rules:

    $ sudo service ip6tables reload

RHEL-06-000525

CCI-000169

low

Auditing must be enabled at boot by setting a kernel parameter.

Each process on the system carries an "auditable" flag which indicates whether its activities can be audited. Although `auditd` takes care of enabling this for all processes which launch after it does, adding the kernel argument ensures it is set for every process during boot.

If , this is a finding.

To ensure all processes can be audited, even those which start prior to the audit daemon, add the argument `audit=1` to the kernel line in `/etc/grub.conf`, in the manner below:

    kernel /vmlinuz-version ro vga=ext root=/dev/VolGroup00/LogVol00 rhgb quiet audit=1

RHEL-06-000526

CCI-000366

low

Automated file system mounting tools must not be enabled unless needed.

Disabling the automounter permits the administrator to statically control filesystem mounting through `/etc/fstab`.

If , this is a finding.

The `autofs` daemon mounts and unmounts filesystems, such as user home directories shared via NFS, on demand. In addition, autofs can be used to handle removable media, and the default configuration provides the cdrom device as `/misc/cd`. However, this method of providing access to removable media is not common, so autofs can almost always be disabled if NFS is not in use. Even if NFS is required, it may be possible to configure filesystem mounts statically by editing `/etc/fstab` rather than relying on the automounter.
The `autofs` service can be disabled with the following command:

    $ sudo chkconfig autofs off