Detection: Suspicious Ticket Granting Ticket Request

Description

The following analytic detects suspicious Kerberos Ticket Granting Ticket (TGT) requests that may indicate exploitation of CVE-2021-42278 and CVE-2021-42287. It leverages Event ID 4781 (account name change) and Event ID 4768 (TGT request) to identify sequences where a newly renamed computer account requests a TGT. This behavior is significant as it could represent an attempt to escalate privileges by impersonating a Domain Controller. If confirmed malicious, this activity could allow attackers to gain elevated access and potentially control over the domain environment.

Search

1`wineventlog_security` (EventCode=4781 OldTargetUserName="*$" NewTargetUserName!="*$") OR (EventCode=4768 TargetUserName!="*$") 
2| eval RenamedComputerAccount = coalesce(NewTargetUserName, TargetUserName) 
3| transaction RenamedComputerAccount startswith=(EventCode=4781) endswith=(EventCode=4768) 
4| eval short_lived=case((duration<2),"TRUE") 
5| search short_lived = TRUE 
6| table _time, Computer, EventCode, TargetUserName, RenamedComputerAccount, short_lived 
7| rename Computer as dest 
8| `suspicious_ticket_granting_ticket_request_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4768	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'
Windows Event Log Security 4781	Windows	'xmlwineventlog'	'XmlWinEventLog:Security'

Macros Used

Annotations

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Implementation

To successfully implement this search, you need to be ingesting Domain Controller and Kerberos events. The Advanced Security Audit policy setting Audit Kerberos Authentication Service within Account Logon needs to be enabled.

Known False Positives

A computer account name change event inmediately followed by a kerberos TGT request with matching fields is unsual. However, legitimate behavior may trigger it. Filter as needed.

Associated Analytic Story

• Active Directory Kerberos Attacks

• Active Directory Privilege Escalation

• sAMAccountName Spoofing and Domain Controller Impersonation

Risk Based Analytics (RBA)

References

• https://exploit.ph/cve-2021-42287-cve-2021-42278-weaponisation.html

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42278

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-42287

Detection Testing

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 5