Emerging Threathightest

Suspicious Sysmon as Execution Parent

Detects suspicious process executions in which Sysmon itself is the parent of a process, which could be a sign of exploitation (e.g. CVE-2022-41120)

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Launch

Florian Roth (Nextron Systems), Tim Shelton (fp werfault)Created Thu Nov 10Updated Fri Jul 046d1058a4-407e-4f3a-a144-1968c11dc5c32022

Emerging Threat

Active Threat

Developed to detect an active or emerging threat. Prioritize investigation of any alerts and correlate with threat intelligence.

Log Source

WindowsProcess Creation

ProductWindows← raw: windows

CategoryProcess Creation← raw: process_creation

Events generated when a new process is spawned on the system. Covers command-line arguments, parent/child relationships, and process metadata.

Detection Logic

detection:
    selection:
        ParentImage|endswith:
            - '\Sysmon.exe'
            - '\Sysmon64.exe'
    filter_main_temp_sysmon:
        # C:\Users\ADMINI~1\AppData\Local\Temp\2\Sysmon.exe
        Image|startswith: 'C:\Users\'
        Image|contains: '\AppData\Local\Temp\'
        Image|endswith:
            - '\Sysmon.exe'
            - '\Sysmon64.exe'
    filter_main_generic:
        Image|contains:
            - ':\Windows\Sysmon.exe'
            - ':\Windows\Sysmon64.exe'
            - ':\Windows\System32\conhost.exe'
            - ':\Windows\System32\WerFault.exe' # When Sysmon crashes
            - ':\Windows\System32\WerFaultSecure.exe' # When Sysmon crashes
            - ':\Windows\System32\wevtutil.exe'
            - ':\Windows\SysWOW64\wevtutil.exe'
    filter_main_null:
        Image: null
    condition: selection and not 1 of filter_main_*