Pass-the-ticket is an authentication exploit which involves using stolen Kerberos tickets to authenticate to a domain without the account’s password. Also known as the forged ticket attack, it is one of the common and effective techniques to move laterally within a network.
The valid Kerberos tickets can be extracted from the lsass memory on a system. Depending on the level of access in a system, the attacker can get hold of the user’s service tickets or ticket granting ticket (TGT) . While the TGT can be used to get the required service tickets from the Ticket Granting Server, the service tickets are the actual key to access specific critical server or service in the network.
The two popular exploits in this technique are Silver ticket and Golden ticket. Silver Tickets are used to generate service tickets to access a particular service like MS SQL and the system that hosts the service . Golden tickets on the other hand, are used to generate TGTs for any account in Active Directory.
When the attacker steals the NTLM hash of a user account, they can forge silver tickets for all the services to which the user account has access.
On the other hand, if the attacker successfully steals the NTLM hash of the KRBTGT account —service account of the Key Distribution Center (KDC), they can issue TGTs for any account in the domain. Golden ticket is the forged Key Distribution Center (KDC) rather than a ticket.
The various tools that can be used to carry out pass the ticket attack on Windows include mimikatz, rubeus, PSexec etc.
It's difficult to detect these attacks as the events look similar to any other normal authentication process. However, it isn't impossible.
You can monitor your network by auditing all Kerberos authentication events and reviewing for discrepancies. For example, to investigate pass-the-ticket attcak at endpoints, carry out the following steps:
During legitimate authentication to the domain, the following event IDs can be found in this order:
If a request is being made through golden ticket, no request for TGT would be made. This implies that any authentications that log onlyevent ID 4769 and event ID 4770 is an indication of the presence of a golden ticket.
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