cis-ubuntu1604-v200-4-1-4

DevOps & Security

Ensure events that modify user/group information are collected

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Source SKILL.md: https://github.com/CyberStrikeus/CyberStrike/blob/HEAD/.cyberstrike/skill/CIS_benchmarks/Operating_Systems/Ubuntu/CIS_Ubuntu_Linux_16.04_LTS_Benchmark_v2.0.0/cis-ubuntu1604-v200-4-1-4/SKILL.md

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CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Control 4.1.4

Profile

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

Description

Record events affecting the group, passwd (user IDs), shadow and gshadow (passwords) or /etc/security/opasswd (old passwords, based on remember parameter in the PAM configuration) files. The parameters in this section will watch the files to see if they have been opened for write or have had attribute changes (e.g. permissions) and tag them with the identifier "identity" in the audit log file.

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

Rationale

Unexpected changes to these files could be an indication that the system has been compromised and that an unauthorized user is attempting to hide their activities or compromise additional accounts.

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 identity /etc/audit/rules.d/*.rules

Verify the output matches:

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

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

auditctl -l | grep identity

Verify the output matches:

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

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-identity.rules

Add the following lines:

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

Default Value

By default, no audit rules are configured for identity file changes.

References

CIS Ubuntu Linux 16.04 LTS Benchmark v2.0.0 - Section 4.1.4

CIS Controls

Controls Version	Control
v7	4.8 Log and Alert on Changes to Administrative Group Membership - Configure systems to issue a log entry and alert when an account is added to or removed from any group assigned administrative privileges.