PetitPotam Suspicious Kerberos TGT Request

testhigh
log source: windows · securityauthor Mauricio Velazco, Michael Haagdate 2021-09-02
01

description

What this is, in brief.

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.

02

tags

attack.credential-accessattack.t1187
03

rule source (YAML)

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
04

detects techniques (1)

ATT&CK techniques this enables or maps to.

05

references

External citations — patches, advisories, analysis.