NetNTLM Downgrade Attack — Sigma Rule

Rule metadata and linked tags

Author: Florian Roth (Nextron Systems), wagga. Source status: test; severity: high. Source dates: 2018-03-20 / 2022-10-09.

{
  "product": "windows",
  "service": "security",
  "definition": "Requirements: Audit Policy : Object Access > Audit Registry (Success)"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 1b89c65bdbe7cbc4a5aa3a4289e13469bde2fd9c9159af8408fa47751bd5d469

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: NetNTLM Downgrade Attack
id: d3abac66-f11c-4ed0-8acb-50cc29c97eed
related:
    - id: d67572a0-e2ec-45d6-b8db-c100d14b8ef2
      type: derived
status: test
description: Detects NetNTLM downgrade attack
references:
    - https://www.optiv.com/blog/post-exploitation-using-netntlm-downgrade-attacks
author: Florian Roth (Nextron Systems), wagga
date: 2018-03-20
modified: 2022-10-09
tags:
    - attack.persistence
    - attack.defense-impairment
    - attack.t1685
    - attack.t1112
logsource:
    product: windows
    service: security
    definition: 'Requirements: Audit Policy : Object Access > Audit Registry (Success)'
detection:
    selection:
        EventID: 4657
        ObjectName|contains|all:
            - '\REGISTRY\MACHINE\SYSTEM'
            - 'ControlSet'
            - '\Control\Lsa'
        ObjectValueName:
            - 'LmCompatibilityLevel'
            - 'NtlmMinClientSec'
            - 'RestrictSendingNTLMTraffic'
    condition: selection
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://www.optiv.com/blog/post-exploitation-using-netntlm-downgrade-attacks