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CIS Ubuntu 14.04 LTS - 4.1.4 Ensure events that modify date and time information are collected

DevOps & Security
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Collect audit events for system date and time modifications to detect tampering

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4.1.4 Ensure events that modify date and time information are collected (Scored)

Profile Applicability

  • Level 2 - Server
  • Level 2 - Workstation

Description

Capture events where the system date and/or time has been modified. The parameters in this section are set to determine if the adjtimex (tune kernel clock), settimeofday (Set time, using timeval and timezone structures) stime (using seconds since 1/1/1970) or clock_settime (allows for the setting of several internal clocks and timers) system calls have been executed and always write an audit record to the /var/log/audit.log file upon exit, tagging the records with the identifier "time-change".

Rationale

Unexpected changes in system date and/or time could be a sign of malicious activity on the system.

Audit Procedure

On a 32 bit system run the following commands:

grep time-change /etc/audit/audit.rules
auditctl -l | grep time-change

Verify output of both matches:

-a always,exit -F arch=b32 -S adjtimex -S settimeofday -S stime -k time-change
-a always,exit -F arch=b32 -S clock_settime -k time-change
-w /etc/localtime -p wa -k time-change

On a 64 bit system run the following commands:

grep time-change /etc/audit/audit.rules
auditctl -l | grep time-change

Verify output of both matches:

-a always,exit -F arch=b64 -S adjtimex -S settimeofday -k time-change
-a always,exit -F arch=b32 -S adjtimex -S settimeofday -S stime -k time-change
-a always,exit -F arch=b64 -S clock_settime -k time-change
-a always,exit -F arch=b32 -S clock_settime -k time-change
-w /etc/localtime -p wa -k time-change

Expected Result

The audit rules for time-change should be present and active in both the rules file and the running configuration.

Remediation

For 32 bit systems add the following lines to the /etc/audit/audit.rules file:

-a always,exit -F arch=b32 -S adjtimex -S settimeofday -S stime -k time-change
-a always,exit -F arch=b32 -S clock_settime -k time-change
-w /etc/localtime -p wa -k time-change

For 64 bit systems add the following lines to the /etc/audit/audit.rules file:

-a always,exit -F arch=b64 -S adjtimex -S settimeofday -k time-change
-a always,exit -F arch=b32 -S adjtimex -S settimeofday -S stime -k time-change
-a always,exit -F arch=b64 -S clock_settime -k time-change
-a always,exit -F arch=b32 -S clock_settime -k time-change
-w /etc/localtime -p wa -k time-change

Notes: Reloading the auditd config to set active settings may require a system reboot.

Default Value

Not configured by default.

References

  1. CIS Controls v6.1 - 3.6 Implement Automated Configuration Monitoring System

Profile

  • Level 2 - Server
  • Level 2 - Workstation