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Description

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

Annotations

ATT&CK
ID Technique Tactic
T1078 Valid Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
T1078.002 Domain Accounts Defense Evasion, Initial Access, Persistence, Privilege Escalation
Kill Chain Phase
  • Exploitation
NIST
CIS20
CVE
1
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 `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`

Macros

The SPL above uses the following Macros:

:information_source: 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.

Required field

  • _time
  • EventCode
  • Old_Account_Name
  • New_Account_Name
  • Account_Name
  • ComputerName

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

RBA

Risk Score Impact Confidence Message
60.0 100 60 A suspicious TGT was requested was requested

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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

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