Suspicious Kerberos RC4 Ticket Encryption — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems). Source status: test; severity: medium. Source dates: 2017-02-06 / 2022-06-19.

{
  "product": "windows",
  "service": "security"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 6b95365726dfb2744695f0402f9784dc015f027f53543b4db4d0f60527b9b2b8

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: Suspicious Kerberos RC4 Ticket Encryption
id: 496a0e47-0a33-4dca-b009-9e6ca3591f39
status: test
description: Detects service ticket requests using RC4 encryption type
references:
    - https://adsecurity.org/?p=3458
    - https://www.trimarcsecurity.com/single-post/TrimarcResearch/Detecting-Kerberoasting-Activity
author: Florian Roth (Nextron Systems)
date: 2017-02-06
modified: 2022-06-19
tags:
    - attack.credential-access
    - attack.t1558.003
logsource:
    product: windows
    service: security
detection:
    selection:
        EventID: 4769
        TicketOptions: '0x40810000'
        TicketEncryptionType: '0x17'
    reduction:
        ServiceName|endswith: '$'
    condition: selection and not reduction
falsepositives:
    - Service accounts used on legacy systems (e.g. NetApp)
    - Windows Domains with DFL 2003 and legacy systems
level: medium

Original YAML and metadata in JSON

False positives

• Service accounts used on legacy systems (e.g. NetApp)
• Windows Domains with DFL 2003 and legacy systems

Source references

• https://adsecurity.org/?p=3458
• https://www.trimarcsecurity.com/single-post/TrimarcResearch/Detecting-Kerberoasting-Activity