cis-ubuntu1604-v200-4-1-17

DevOps & Security

Ensure the audit configuration is immutable

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 4.1.17

Profile

Level: 2 - Server
Level: 2 - Workstation
Assessment Status: Automated

Description

Set system audit so that audit rules cannot be modified with auditctl. Setting the flag "-e 2" forces audit to be put in immutable mode. Audit changes can only be made on system reboot.

Note: Reloading the auditd config to set active settings requires the auditd service to be restarted, and may require a system reboot.

Rationale

In immutable mode, unauthorized users cannot execute changes to the audit system to potentially hide malicious activity and then put the audit rules back. Users would most likely notice a system reboot and that could alert administrators of an attempt to make unauthorized audit changes.

Impact

Any changes to the audit configuration will require a system reboot to take effect.

Audit Procedure

Command Line

Run the following command and verify output matches:

grep "^\s*[^#]" /etc/audit/rules.d/*.rules | tail -1

Expected Result

-e 2

The last line in the rules should be -e 2.

Remediation

Command Line

Edit or create a file in the /etc/audit/rules.d/ directory ending in .rules and add the following line at the end of the file:

-e 2

Note: This must be the last line in the last rules file loaded. Ensure that it is in a file that will be loaded after all other rules files (e.g. 99-finalize.rules).

Default Value

By default, the audit configuration is not immutable.

References

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Section 4.1.17

CIS Controls

Controls Version	Control
v7	6.2 Activate audit logging - Ensure that local logging has been enabled on all systems and networking devices.
v7	6.3 Enable Detailed Logging - Enable system logging to include detailed information such as an event source, date, user, timestamp, source addresses, destination addresses, and other useful elements.