Steal or Forge Kerberos Tickets: Silver Ticket
Adversaries who have the password hash of a target service account (e.g. SharePoint, MSSQL) may forge Kerberos ticket granting service (TGS) tickets, also known as silver tickets. Kerberos TGS tickets are also known as service tickets.
Silver tickets are more limited in scope in than golden tickets in that they only enable adversaries to access a particular resource (e.g. MSSQL) and the system that hosts the resource; however, unlike golden tickets, adversaries with the ability to forge silver tickets are able to create TGS tickets without interacting with the Key Distribution Center (KDC), potentially making detection more difficult.
|Encrypt Sensitive Information||
Enable AES Kerberos encryption (or another stronger encryption algorithm), rather than RC4, where possible.
Ensure strong password length (ideally 25+ characters) and complexity for service accounts and that these passwords periodically expire. Also consider using Group Managed Service Accounts or another third party product such as password vaulting.
|Privileged Account Management||
Limit service accounts to minimal required privileges, including membership in privileged groups such as Domain Administrators.
Monitor for anomalous Kerberos activity, such as malformed or blank fields in Windows logon/logoff events (Event ID 4624, 4634, 4672).
Monitor for unexpected processes interacting with lsass.exe. Common credential dumpers such as Mimikatz access the LSA Subsystem Service (LSASS) process by opening the process, locating the LSA secrets key, and decrypting the sections in memory where credential details, including Kerberos tickets, are stored.
- Sean Metcalf. (2015, November 17). How Attackers Use Kerberos Silver Tickets to Exploit Systems. Retrieved February 27, 2020.
- Metcalf, S. (2015, May 03). Detecting Forged Kerberos Ticket (Golden Ticket & Silver Ticket) Use in Active Directory. Retrieved December 23, 2015.
- Metcalf, S. (2015, December 31). Cracking Kerberos TGS Tickets Using Kerberoast – Exploiting Kerberos to Compromise the Active Directory Domain. Retrieved March 22, 2018.