Detection: Suspicious Kerberos Service Ticket Request

Description

The following analytic detects suspicious Kerberos Service Ticket (TGS) requests where the requesting account name matches the service name, potentially indicating an exploitation attempt of CVE-2021-42278 and CVE-2021-42287. This detection leverages Event ID 4769 from Domain Controller and Kerberos events. Such activity is significant as it may represent an adversary attempting to escalate privileges by impersonating a domain controller. If confirmed malicious, this could allow an attacker to take control of the domain controller, leading to complete domain compromise and unauthorized access to sensitive information.

Search

1`wineventlog_security` EventCode=4769 
2| eval isSuspicious = if(lower(ServiceName) = lower(mvindex(split(TargetUserName,"@"),0)),1,0) 
3| where isSuspicious = 1 
4| rename Computer as dest
5| rename TargetUserName as user 
6| table _time, dest, src_ip, user, ServiceName, Error_Code, isSuspicious 
7| `suspicious_kerberos_service_ticket_request_filter`

Data Source

Name	Platform	Sourcetype	Source
Windows Event Log Security 4769	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

We have tested this detection logic with ~2 million 4769 events and did not identify false positives. However, they may be possible in certain environments. 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

• https://docs.microsoft.com/en-us/openspecs/windows_protocols/ms-sfu/02636893-7a1f-4357-af9a-b672e3e3de13

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