cis-ubuntu2004-v300-6-3-2-4

DevOps & Security

Ensure system warns when audit logs are low on space

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6.3.2.4 Ensure system warns when audit logs are low on space (Automated)

Profile

Level 2 - Server
Level 2 - Workstation

Description

The auditd daemon can be configured to halt the system, put the system in single user mode or send a warning message, if the partition that holds the audit log files is low on space.

The space_left_action parameter tells the system what action to take when the system has detected that it is starting to get low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt.

The admin_space_left_action parameter tells the system what action to take when the system has detected that it is low on disk space. Valid values are ignore, syslog, rotate, email, exec, suspend, single, and halt.

Rationale

In high security contexts, the risk of detecting unauthorized access or nonrepudiation exceeds the benefit of the system's availability.

Impact

If the admin_space_left_action is set to single the audit daemon will put the computer system in single user mode.

Audit Procedure

Command Line

Run the following command and verify the space_left_action is set to email, exec, single, or halt:

grep -P -- '^\h*space_left_action\h*=\h*(email|exec|single|halt)\b' /etc/audit/auditd.conf

Verify the output is email, exec, single, or halt.

Example output:

space_left_action = email

Run the following command and verify the admin_space_left_action is set to single - OR - halt:

grep -P -- '^\h*admin_space_left_action\h*=\h*(single|halt)\b' /etc/audit/auditd.conf

Verify the output is single or halt.

Example output:

admin_space_left_action = single

Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email

Expected Result

space_left_action should be set to email, exec, single, or halt. admin_space_left_action should be set to single or halt.

Remediation

Command Line

Set the space_left_action parameter in /etc/audit/auditd.conf to email, exec, single, or halt:

Example:

space_left_action = email

Set the admin_space_left_action parameter in /etc/audit/auditd.conf to single or halt:

Example:

admin_space_left_action = single

Note: A Mail Transfer Agent (MTA) must be installed and configured properly to set space_left_action = email

References

NIST SP 800-53 Rev. 5: AU-2, AU-8, AU-12, SI-5
AUDITD.CONF(5)

CIS Controls

Controls Version	Control	IG 1	IG 2	IG 3
v8	8.2 Collect Audit Logs	X	X	X
v8	8.3 Ensure Adequate Audit Log Storage	X	X	X
v7	6.2 Activate audit logging	X	X	X

MITRE ATT&CK Mappings: T1562, T1562.006 / TA0005