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Description

The following analytic detects a suspicious Kerberos Ticket Granting Ticket (TGT) request, identified by Event Code 4768. This detection leverages Windows Security Event Logs to identify TGT requests with unusual fields, which may indicate the use of tools like Rubeus following the exploitation of CVE-2021-36942 (PetitPotam). This activity is significant as it can signal an attacker leveraging a compromised certificate to request Kerberos tickets, potentially leading to unauthorized access. If confirmed malicious, this could allow attackers to escalate privileges and persist within the environment, posing a severe security risk.

  • Type: TTP

  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud

  • Last Updated: 2024-05-30
  • Author: Michael Haag, Mauricio Velazco, Splunk
  • ID: e3ef244e-0a67-11ec-abf2-acde48001122

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1003 OS Credential Dumping Credential Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


1
2
3
4
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`wineventlog_security` EventCode=4768 src!="::1" TargetUserName=*$ CertThumbprint!="" 
| stats count min(_time) as firstTime max(_time) as lastTime by dest, TargetUserName, src, action 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `petitpotam_suspicious_kerberos_tgt_request_filter`

Macros

The SPL above uses the following Macros:

:information_source: petitpotam_suspicious_kerberos_tgt_request_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • dest
  • Account_Name
  • Client_Address
  • action
  • Message

How To Implement

The following analytic requires Event Code 4768. Ensure that it is logging no Domain Controllers and appearing in Splunk.

Known False Positives

False positives are possible if the environment is using certificates for authentication.

Associated Analytic Story

RBA

Risk Score Impact Confidence Message
56.0 80 70 A Kerberos TGT was requested in a non-standard manner against $dest$, potentially related to CVE-2021-36942, PetitPotam.

: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

source | version: 3