Potential Remote Desktop Connection to Non-Domain Host — Sigma Rule

Rule metadata and linked tags

Author: James Pemberton. Source status: test; severity: medium. Source dates: 2020-05-22 / 2021-11-27.

{
  "product": "windows",
  "service": "ntlm",
  "definition": "Requires events from Microsoft-Windows-NTLM/Operational"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 8d2eea9c58998e82ba4885cb5d7114cb0eb2fbc2f70ca487c2fe61f75fb0e2ac

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: Potential Remote Desktop Connection to Non-Domain Host
id: ce5678bb-b9aa-4fb5-be4b-e57f686256ad
status: test
description: Detects logons using NTLM to hosts that are potentially not part of the domain.
references:
    - n/a
author: James Pemberton
date: 2020-05-22
modified: 2021-11-27
tags:
    - attack.command-and-control
    - attack.t1219.002
logsource:
    product: windows
    service: ntlm
    definition: Requires events from Microsoft-Windows-NTLM/Operational
detection:
    selection:
        EventID: 8001
        TargetName|startswith: 'TERMSRV'
    condition: selection
falsepositives:
    - Host connections to valid domains, exclude these.
    - Host connections not using host FQDN.
    - Host connections to external legitimate domains.
level: medium

Original YAML and metadata in JSON

False positives

• Host connections to valid domains, exclude these.
• Host connections not using host FQDN.
• Host connections to external legitimate domains.

Source references

• n/a (source note; no public URL supplied)