Suspicious Eventlog Clear

Title: Suspicious Eventlog Clear
Status: test
Description:Detects usage of known powershell cmdlets such as "Clear-EventLog" to clear the Windows event logs
References:
  -https://twitter.com/oroneequalsone/status/1568432028361830402
  -https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1070.001/T1070.001.md
  -https://eqllib.readthedocs.io/en/latest/analytics/5b223758-07d6-4100-9e11-238cfdd0fe97.html
  -https://stackoverflow.com/questions/66011412/how-to-clear-a-event-log-in-powershell-7
  -https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.eventing.reader.eventlogsession.clearlog?view=windowsdesktop-9.0&viewFallbackFrom=dotnet-plat-ext-5.0#System_Diagnostics_Eventing_Reader_EventLogSession_ClearLog_System_String_
  -https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.eventlog.clear
Author: Nasreddine Bencherchali (Nextron Systems), Swachchhanda Shrawan Poudel (Nextron Systems)
Date: 2022-09-12
modified:2025-10-06
Tags:

• -'attack.defense-impairment'
• -'attack.t1685.005'

Logsource:

• product: windows
• category: ps_script
• definition: Requirements: Script Block Logging must be enabled

Detection:
  selection:
    - ScriptBlockText|contains:
      - 'Clear-EventLog '
      - 'Remove-EventLog '
      - 'Limit-EventLog '
      - 'Clear-WinEvent '
    - ScriptBlockText|contains|all:
      - 'Eventing.Reader.EventLogSession'
      - 'ClearLog'
    - ScriptBlockText|contains|all:
      - 'Diagnostics.EventLog'
      - 'Clear'
  condition:selection
Falsepositives:
  -Rare need to clear logs before doing something. Sometimes used by installers or cleaner scripts. The script should be investigated to determine if it's legitimate
Level: medium