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Suspicious Eventlog Clearing or Configuration Change Activity

SIGMA detection rule by Ecco, Daniil Yugoslavskiy, oscd.community, D3F7A5105, Swachchhanda Shrawan Poudel (Nextron Systems) · GPL-2.0

Detects the clearing or configuration tampering of EventLog using utilities such as "wevtutil", "powershell" and "wmic". This technique were seen used by threat actors and ransomware strains in order to evade defenses.

title: Suspicious Eventlog Clearing or Configuration Change Activity
id: 676111e7-0d6f-b5f4-e267-6399b5052fdc
related:
    - id: cc36992a-4671-4f21-a91d-6c2b72a2edf5
      type: derived
status: stable
description: |
    Detects the clearing or configuration tampering of EventLog using utilities such as "wevtutil", "powershell" and "wmic".
    This technique were seen used by threat actors and ransomware strains in order to evade defenses.
references:
    - 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://learn.microsoft.com/en-us/windows-server/administration/windows-commands/wevtutil
    - https://gist.github.com/fovtran/ac0624983c7722e80a8f5a4babb170ee
    - https://jdhnet.wordpress.com/2017/12/19/changing-the-location-of-the-windows-event-logs/
    - https://www.linkedin.com/posts/huntress-labs_when-a-sketchy-incident-hits-your-network-activity-7304940371078238208-Th_l/?utm_source=share&utm_medium=member_desktop&rcm=ACoAAAJTlRcB28IaUtg03HUU-IdliwzoAL1flGc
    - 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: Ecco, Daniil Yugoslavskiy, oscd.community, D3F7A5105, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2019-09-26
modified: 2025-03-12
tags:
    - attack.defense-impairment
    - attack.t1685.005
    - attack.t1685.001
    - car.2016-04-002
logsource:
    category: process_creation
    product: windows
detection:
    process_creation:
        EventID: 4688
        Channel: Security
    selection_wevtutil_img:
        - NewProcessName|endswith: \wevtutil.exe
        - OriginalFileName: wevtutil.exe
    selection_wevtutil_cmd:
        CommandLine|contains:
            - 'clear-log '          # clears specified log
            - ' cl '                # short version of 'clear-log'
            - 'set-log '            # modifies config of specified log. could be uset to set it to a tiny size
            - ' sl '                # short version of 'set-log'
            - 'lfn:'                # change log file location and name
    selection_other_ps_img:
        NewProcessName|endswith:
            - \powershell.exe
            - \powershell_ise.exe
            - \pwsh.exe
    selection_other_ps_cmd:
        - CommandLine|contains:
              - 'Clear-EventLog '
              - 'Remove-EventLog '
              - 'Limit-EventLog '
              - 'Clear-WinEvent '
        - CommandLine|contains|all:
              - Eventing.Reader.EventLogSession   # [System.Diagnostics.Eventing.Reader.EventLogSession]::GlobalSession.ClearLog($_.LogName)
              - ClearLog
        - CommandLine|contains|all:
              - Diagnostics.EventLog
              - Clear
    selection_other_wmi:
        CommandLine|contains: ClearEventLog
        NewProcessName|endswith:
            - \powershell.exe
            - \powershell_ise.exe
            - \pwsh.exe
            - \wmic.exe
    filter_main_msiexec:
        # Example seen during office update/installation:
        #   ParentImage: C:\Windows\SysWOW64\msiexec.exe
        #   CommandLine: "C:\WINDOWS\system32\wevtutil.exe" sl Microsoft-RMS-MSIPC/Debug /q:true /e:true /l:4 /rt:false
        CommandLine|contains: ' sl '
        ParentProcessName:
            - C:\Windows\SysWOW64\msiexec.exe
            - C:\Windows\System32\msiexec.exe
    condition: process_creation and ((all of selection_wevtutil_*) or (all of selection_other_ps_*) or (selection_other_wmi) and not 1 of filter_main_*)
falsepositives:
    - Admin activity
    - Scripts and administrative tools used in the monitored environment
    - Maintenance activity
level: high
ruletype: Sigma

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