Use Alternate Authentication Material: Pass the Ticket
Adversaries may "pass the ticket" using stolen Kerberos tickets to move laterally within an environment, bypassing normal system access controls. Pass the ticket (PtT) is a method of authenticating to a system using Kerberos tickets without having access to an account's password. Kerberos authentication can be used as the first step to lateral movement to a remote system.
When preforming PtT, valid Kerberos tickets for Valid Accounts are captured by OS Credential Dumping. A user's service tickets or ticket granting ticket (TGT) may be obtained, depending on the level of access. A service ticket allows for access to a particular resource, whereas a TGT can be used to request service tickets from the Ticket Granting Service (TGS) to access any resource the user has privileges to access.
A Silver Ticket can be obtained for services that use Kerberos as an authentication mechanism and are used to generate tickets to access that particular resource and the system that hosts the resource (e.g., SharePoint).
Adversaries may also create a valid Kerberos ticket using other user information, such as stolen password hashes or AES keys. For example, "overpassing the hash" involves using a NTLM password hash to authenticate as a user (i.e. Pass the Hash) while also using the password hash to create a valid Kerberos ticket.
|M1015||Active Directory Configuration||
To contain the impact of a previously generated golden ticket, reset the built-in KRBTGT account password twice, which will invalidate any existing golden tickets that have been created with the KRBTGT hash and other Kerberos tickets derived from it. For each domain, change the KRBTGT account password once, force replication, and then change the password a second time. Consider rotating the KRBTGT account password every 180 days.
Ensure that local administrator accounts have complex, unique passwords.
|M1026||Privileged Account Management||
Limit domain admin account permissions to domain controllers and limited servers. Delegate other admin functions to separate accounts.
|M1018||User Account Management||
Do not allow a user to be a local administrator for multiple systems.
Audit all Kerberos authentication and credential use events and review for discrepancies. Unusual remote authentication events that correlate with other suspicious activity (such as writing and executing binaries) may indicate malicious activity.
Event ID 4769 is generated on the Domain Controller when using a golden ticket after the KRBTGT password has been reset twice, as mentioned in the mitigation section. The status code 0x1F indicates the action has failed due to "Integrity check on decrypted field failed" and indicates misuse by a previously invalidated golden ticket.
- Metcalf, S. (2014, November 22). Mimikatz and Active Directory Kerberos Attacks. Retrieved June 2, 2016.
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- Campbell, C. (2014). The Secret Life of Krbtgt. Retrieved December 4, 2014.
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- The Australian Cyber Security Centre (ACSC), the Canadian Centre for Cyber Security (CCCS), the New Zealand National Cyber Security Centre (NZ NCSC), CERT New Zealand, the UK National Cyber Security Centre (UK NCSC) and the US National Cybersecurity and Communications Integration Center (NCCIC). (2018, October 11). Joint report on publicly available hacking tools. Retrieved March 11, 2019.
- Nicolas Verdier. (n.d.). Retrieved January 29, 2018.
- Symantec Security Response. (2015, July 13). “Forkmeiamfamous”: Seaduke, latest weapon in the Duke armory. Retrieved July 22, 2015.
- Sean Metcalf. (2014, November 10). Kerberos & KRBTGT: Active Directory’s Domain Kerberos Service Account. Retrieved January 30, 2020.
- UCF. (n.d.). The password for the krbtgt account on a domain must be reset at least every 180 days. Retrieved November 5, 2020.
- Abolins, D., Boldea, C., Socha, K., Soria-Machado, M. (2016, April 26). Kerberos Golden Ticket Protection. Retrieved July 13, 2017.