Sigma rule: Valid Users Failing to Authenticate from Single Source Using NTLM

A detection rule from the SigmaHQ repository, shown as its author published it. Dataset version ref-13510b25808c, updated 2023-03-13T00:00:00.000Z.

Rule

Title
Valid Users Failing to Authenticate from Single Source Using NTLM
Status
unsupported
Level
medium
Author
Mauricio Velazco
Date
2021/06/01
Modified
2023/03/13
File
unsupported/windows/win_security_susp_failed_logons_single_source_ntlm.yml
Commit
ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects failed logins with multiple valid domain accounts from a single source system using the NTLM protocol.

Log source

product
windows
service
security

Detection

selection1:
    EventID: 4776
    Status: '*0xC000006A' #Account logon with misspelled or bad password.
filter:
    TargetUserName: '*$'
timeframe: 24h
condition: selection1 and not filter | count(TargetUserName) by Workstation > 10

False positives (as the rule lists them)

  • Terminal servers
  • Jump servers
  • Other multiuser systems like Citrix server farms
  • Workstations with frequently changing users

Tags

  • attack.t1110.003
  • attack.initial_access
  • attack.privilege_escalation

MITRE ATT&CK ids this rule names

References

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

Sources and licences

  • SigmaHQ

    "Valid Users Failing to Authenticate from Single Source Using NTLM" by Mauricio Velazco (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/unsupported/windows/win_security_susp_failed_logons_single_source_ntlm.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: Valid Users Failing to Authenticate from Single Source Using NTLM",
entity page, dataset version ref-13510b25808c, updated 2023-03-13T00:00:00.000Z,
https://ransomware-tracker.com/detections/sigma/f88bab7f-b1f4-41bb-bdb1-4b8af35b0470 (accessed 2026-11-03).
Underlying source: SigmaHQ rule f88bab7f-b1f4-41bb-bdb1-4b8af35b0470, 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.