cis-ubuntu1604-v200-4-1-6

DevOps & Security

Ensure events that modify the system's Mandatory Access Controls are collected

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 4.1.6

Profile

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

Description

Monitor AppArmor mandatory access controls. The parameters below monitor any write access (potential additional, deletion or modification of files in the directory) or attribute changes to /etc/apparmor and /etc/apparmor.d directories.

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

Rationale

Changes to files in these directories could indicate that an unauthorized user is attempting to modify access controls and change security contexts, leading to a compromise of the system.

Impact

None.

Audit Procedure

Command Line

Run the following command to verify the rules are contained in a .rules file in the /etc/audit/rules.d/ directory:

grep MAC-policy /etc/audit/rules.d/*.rules

Verify output matches:

-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy

Run the following command to verify that rules are in the running auditd config:

auditctl -l | grep MAC-policy

Verify output matches:

-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy

Expected Result

Output should match the rules listed above.

Remediation

Command Line

Edit or create a file in the /etc/audit/rules.d/ directory ending in .rules.

Example: vi /etc/audit/rules.d/50-MAC-policy.rules

Add the following lines:

-w /etc/apparmor/ -p wa -k MAC-policy
-w /etc/apparmor.d/ -p wa -k MAC-policy

Default Value

By default, no audit rules are configured for MAC policy changes.

References

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Section 4.1.6

CIS Controls

Controls Version	Control
v7	5.5 Implement Automated Configuration Monitoring Systems - Utilize a Security Content Automation Protocol (SCAP) compliant configuration monitoring system to verify all security configuration elements, catalog approved exceptions, and alert when unauthorized changes occur.