Title

The computer clock synchronization tolerance must be limited to 5 minutes or less. (Cat II impact)

Discussion

This setting determines the maximum time difference (in minutes) that Kerberos will tolerate between the time on a client's clock and the time on a server's clock while still considering the two clocks synchronous. In order to prevent replay attacks, Kerberos uses timestamps as part of its protocol definition. For timestamps to work properly, the clocks of the client and the server need to be in sync as much as possible.

Check Content

Verify the following is configured in the Default Domain Policy. Open "Group Policy Management". Navigate to "Group Policy Objects" in the Domain being reviewed (Forest >> Domains >> Domain). Right click on the "Default Domain Policy", select "Edit". Navigate to Computer Configuration >> Policies >> Windows Settings >> Security Settings >> Account Policies >> Kerberos Policy. If the "Maximum tolerance for computer clock synchronization" is greater than "5" minutes, this is a finding.

Fix Text

Configure the policy value in the Default Domain Policy for Computer Configuration >> Windows Settings >> Security Settings >> Account Policies >> Kerberos Policy >> "Maximum tolerance for computer clock synchronization" to "5" minutes or less.

Additional Identifiers

Rule ID: SV-28505r2_rule

Vulnerability ID: V-2380

Group Title: Kerberos - Computer Clock Sync

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.