As part of the sAMAccountName Spoofing (CVE-2021-42278) and Domain Controller Impersonation (CVE-2021-42287) exploitation chain, adversaries will need to request a Kerberos Ticket Granting Ticket (TGT) on behalf of the newly created and renamed computer account. The TGT request will be preceded by a computer account name event. This analytic leverages Event Id 4781,
The name of an account was changed and event Id 4768
A Kerberos authentication ticket (TGT) was requested to correlate a sequence of events where the new computer account on event id 4781 matches the request account on event id 4768. This behavior could represent an exploitation attempt of CVE-2021-42278 and CVE-2021-42287 for privilege escalation.
- Type: Hunting
- Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
- Datamodel: Endpoint
- Last Updated: 2021-12-21
- Author: Mauricio Velazco, Splunk
- ID: d77d349e-6269-11ec-9cfe-acde48001122
Kill Chain Phase
1 2 3 4 5 6 7 `wineventlog_security` (EventCode=4781 Old_Account_Name="*$" New_Account_Name!="*$") OR (EventCode=4768 Account_Name!="*$") | eval RenamedComputerAccount = coalesce(New_Account_Name, mvindex(Account_Name,0)) | transaction RenamedComputerAccount startswith=(EventCode=4781) endswith=(EventCode=4768) | eval short_lived=case((duration<2),"TRUE") | search short_lived = TRUE | table _time, ComputerName, EventCode, Account_Name,RenamedComputerAccount, short_lived |`suspicious_ticket_granting_ticket_request_filter`
The SPL above uses the following Macros:
suspicious_ticket_granting_ticket_request_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
List of fields required to use this analytic.
How To Implement
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
|60.0||100||60||A suspicious TGT was requested was requested|
The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.
source | version: 1