Title

The Kerberos user ticket lifetime must be limited to a maximum of 10 hours or less. (Cat II impact)

Discussion

In Kerberos, there are 2 types of tickets: Ticket Granting Tickets (TGTs) and Service Tickets. Kerberos tickets have a limited lifetime so the time an attacker has to implement an attack is limited. This policy controls how long TGTs can be renewed. With Kerberos, the user’s initial authentication to the domain controller results in a TGT which is then used to request Service Tickets to resources. Upon startup, each computer gets a TGT before requesting a service ticket to the domain controller and any other computers it needs to access. For services that startup under a specified user account, users must always get a TGT first, then get Service Tickets to all computers and services accessed.

Check Content

Fix Text

Set the Kerberos policy option "Maximum lifetime for user ticket" to a maximum of 10 hours, but not 0 which equates to “Ticket doesn’t expire”.

Additional Identifiers

Rule ID: SV-36180r1_rule

Vulnerability ID: V-2378

Group Title: AD.4031 Kerberos - User Ticket Lifetime

Expert Comments

CCIs tied to check.

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