Detectionhightest

PowerShell Base64 Encoded WMI Classes

Detects calls to base64 encoded WMI class such as "Win32_ShadowCopy", "Win32_ScheduledJob", etc.

Convert In Phoenix Studio

Open this Sigma rule in the converter with the YAML preloaded and ready for backend selection.

Christian Burkard (Nextron Systems), Nasreddine Bencherchali (Nextron Systems)Created Mon Jan 301816994b-42e1-4fb1-afd2-134d88184f71windows

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_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cli_shadowcopy:
        # Win32_ShadowCopy
        CommandLine|contains:
            - 'VwBpAG4AMwAyAF8AUwBoAGEAZABvAHcAYwBvAHAAeQ'
            - 'cAaQBuADMAMgBfAFMAaABhAGQAbwB3AGMAbwBwAHkA'
            - 'XAGkAbgAzADIAXwBTAGgAYQBkAG8AdwBjAG8AcAB5A'
            - 'V2luMzJfU2hhZG93Y29we'
            - 'dpbjMyX1NoYWRvd2NvcH'
            - 'XaW4zMl9TaGFkb3djb3B5'
    selection_cli_scheduledJob:
        # Win32_ScheduledJob
        CommandLine|contains:
            - 'VwBpAG4AMwAyAF8AUwBjAGgAZQBkAHUAbABlAGQASgBvAGIA'
            - 'cAaQBuADMAMgBfAFMAYwBoAGUAZAB1AGwAZQBkAEoAbwBiA'
            - 'XAGkAbgAzADIAXwBTAGMAaABlAGQAdQBsAGUAZABKAG8AYg'
            - 'V2luMzJfU2NoZWR1bGVkSm9i'
            - 'dpbjMyX1NjaGVkdWxlZEpvY'
            - 'XaW4zMl9TY2hlZHVsZWRKb2'
    selection_cli_process:
        # Win32_Process
        CommandLine|contains:
            - 'VwBpAG4AMwAyAF8AUAByAG8AYwBlAHMAcw'
            - 'cAaQBuADMAMgBfAFAAcgBvAGMAZQBzAHMA'
            - 'XAGkAbgAzADIAXwBQAHIAbwBjAGUAcwBzA'
            - 'V2luMzJfUHJvY2Vzc'
            - 'dpbjMyX1Byb2Nlc3'
            - 'XaW4zMl9Qcm9jZXNz'
    selection_cli_useraccount:
        # Win32_UserAccount
        CommandLine|contains:
            - 'VwBpAG4AMwAyAF8AVQBzAGUAcgBBAGMAYwBvAHUAbgB0A'
            - 'cAaQBuADMAMgBfAFUAcwBlAHIAQQBjAGMAbwB1AG4AdA'
            - 'XAGkAbgAzADIAXwBVAHMAZQByAEEAYwBjAG8AdQBuAHQA'
            - 'V2luMzJfVXNlckFjY291bn'
            - 'dpbjMyX1VzZXJBY2NvdW50'
            - 'XaW4zMl9Vc2VyQWNjb3Vud'
    selection_cli_loggedonuser:
        # Win32_LoggedOnUser
        CommandLine|contains:
            - 'VwBpAG4AMwAyAF8ATABvAGcAZwBlAGQATwBuAFUAcwBlAHIA'
            - 'cAaQBuADMAMgBfAEwAbwBnAGcAZQBkAE8AbgBVAHMAZQByA'
            - 'XAGkAbgAzADIAXwBMAG8AZwBnAGUAZABPAG4AVQBzAGUAcg'
            - 'V2luMzJfTG9nZ2VkT25Vc2Vy'
            - 'dpbjMyX0xvZ2dlZE9uVXNlc'
            - 'XaW4zMl9Mb2dnZWRPblVzZX'
    condition: selection_img and 1 of selection_cli_*