Suspicious Eventlog Clear

calendar Apr 16, 2025 · attack.defense-evasion attack.t1070.001  ·
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Detects usage of known powershell cmdlets such as "Clear-EventLog" to clear the Windows event logs

Sigma rule (View on GitHub)

 1title: Suspicious Eventlog Clear
 2id: 0f017df3-8f5a-414f-ad6b-24aff1128278
 3related:
 4    - id: cc36992a-4671-4f21-a91d-6c2b72a2edf5
 5      type: derived
 6status: test
 7description: Detects usage of known powershell cmdlets such as "Clear-EventLog" to clear the Windows event logs
 8references:
 9    - https://twitter.com/oroneequalsone/status/1568432028361830402
10    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1070.001/T1070.001.md
11    - https://eqllib.readthedocs.io/en/latest/analytics/5b223758-07d6-4100-9e11-238cfdd0fe97.html
12    - https://stackoverflow.com/questions/66011412/how-to-clear-a-event-log-in-powershell-7
13    - 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_
14    - https://learn.microsoft.com/en-us/dotnet/api/system.diagnostics.eventlog.clear
15author: Nasreddine Bencherchali (Nextron Systems), Swachchhanda Shrawan Poudel (Nextron Systems)
16date: 2022-09-12
17modified: 2025-03-12
18tags:
19    - attack.defense-evasion
20    - attack.t1070.001
21logsource:
22    product: windows
23    category: ps_script
24    definition: 'Requirements: Script Block Logging must be enabled'
25detection:
26    selection:
27        - ScriptBlockText|contains:
28              - 'Clear-EventLog '
29              - 'Remove-EventLog '
30              - 'Limit-EventLog '
31              - 'Clear-WinEvent '
32        - ScriptBlockText|contains|all:
33              - 'Eventing.Reader.EventLogSession' # [System.Diagnostics.Eventing.Reader.EventLogSession]::GlobalSession.ClearLog($_.LogName)
34              - 'ClearLog'
35        - ScriptBlockText|contains:
36              - 'Diagnostics.EventLog'
37              - 'Clear'
38    condition: selection
39falsepositives:
40    - 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
41level: medium

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