PetitPotam Suspicious Kerberos TGT Request — Sigma Rule

Rule metadata and linked tags

Author: Mauricio Velazco, Michael Haag. Source status: test; severity: high. Source dates: 2021-09-02 / 2022-10-05.

{
  "product": "windows",
  "service": "security",
  "definition": "The advanced audit policy setting \"Account Logon > Kerberos Authentication Service\" must be configured for Success/Failure"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: ef0befc88cb8a8b8d0408077e07e0e515701242b0b560a8efc9051ad712ff390

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: PetitPotam Suspicious Kerberos TGT Request
id: 6a53d871-682d-40b6-83e0-b7c1a6c4e3a5
status: test
description: |
    Detect suspicious Kerberos TGT requests.
    Once an attacer obtains a computer certificate by abusing Active Directory Certificate Services in combination with PetitPotam, the next step would be to leverage the certificate for malicious purposes.
    One way of doing this is to request a Kerberos Ticket Granting Ticket using a tool like Rubeus.
    This request will generate a 4768 event with some unusual fields depending on the environment.
    This analytic will require tuning, we recommend filtering Account_Name to the Domain Controller computer accounts.
references:
    - https://github.com/topotam/PetitPotam
    - https://isc.sans.edu/forums/diary/Active+Directory+Certificate+Services+ADCS+PKI+domain+admin+vulnerability/27668/
    - https://github.com/splunk/security_content/blob/88d689fe8a055d8284337b9fad5d9152b42043db/detections/endpoint/petitpotam_suspicious_kerberos_tgt_request.yml
author: Mauricio Velazco, Michael Haag
date: 2021-09-02
modified: 2022-10-05
tags:
    - attack.credential-access
    - attack.t1187
logsource:
    product: windows
    service: security
    definition: 'The advanced audit policy setting "Account Logon > Kerberos Authentication Service" must be configured for Success/Failure'
detection:
    selection:
        EventID: 4768
        TargetUserName|endswith: '$'
        CertThumbprint|contains: '*'
    filter_local:
        IpAddress: '::1'
    filter_thumbprint:
        CertThumbprint: ''
    condition: selection and not 1 of filter_*
falsepositives:
    - False positives are possible if the environment is using certificates for authentication. We recommend filtering Account_Name to the Domain Controller computer accounts.
level: high

Original YAML and metadata in JSON

False positives

• False positives are possible if the environment is using certificates for authentication. We recommend filtering Account_Name to the Domain Controller computer accounts.

Source references

• https://github.com/topotam/PetitPotam
• https://isc.sans.edu/forums/diary/Active+Directory+Certificate+Services+ADCS+PKI+domain+admin+vulnerability/27668/
• https://github.com/splunk/security_content/blob/88d689fe8a055d8284337b9fad5d9152b42043db/detections/endpoint/petitpotam_suspicious_kerberos_tgt_request.yml