Sigma rule: NetNTLM Downgrade Attack

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-4f20f24a3a2e, updated 2022-10-09T00:00:00.000Z.

Rule

Title
NetNTLM Downgrade Attack
Status
test
Level
high
Author
Florian Roth (Nextron Systems), wagga
Date
2018-03-20
Modified
2022-10-09
File
rules/windows/builtin/security/win_security_net_ntlm_downgrade.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects NetNTLM downgrade attack

Log source

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

False positives (as the rule lists them)

  • Unknown

Tags

  • attack.persistence
  • attack.defense-impairment
  • attack.t1685
  • attack.t1112

MITRE ATT&CK ids this rule names

Related rules

References

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/builtin/security/win_security_net_ntlm_downgrade.yml

Sources and licences

  • SigmaHQ

    "NetNTLM Downgrade Attack" by Florian Roth (Nextron Systems), wagga (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/builtin/security/win_security_net_ntlm_downgrade.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

Cite this page

Dragons Eye Ransomware Tracker, "Sigma rule: NetNTLM Downgrade Attack",
entity page, dataset version ref-4f20f24a3a2e, updated 2022-10-09T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/d3abac66-f11c-4ed0-8acb-50cc29c97eed (accessed 2026-11-03).
Underlying source: SigmaHQ rule d3abac66-f11c-4ed0-8acb-50cc29c97eed, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.