Detectionmediumtest

Alternate PowerShell Hosts Pipe

Detects alternate PowerShell hosts potentially bypassing detections looking for powershell.exe

Convert In Phoenix Studio

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

Roberto Rodriguez (Cyb3rWard0g), Tim SheltonCreated Thu Sep 12Updated Tue Oct 0758cb02d5-78ce-4692-b3e1-dce850aae41awindows

Log Source

WindowsNamed Pipe Created

ProductWindows← raw: windows

CategoryNamed Pipe Created← raw: pipe_created

Definition

Note that you have to configure logging for Named Pipe Events in Sysmon config (Event ID 17 and Event ID 18). The basic configuration is in popular sysmon configuration (https://github.com/SwiftOnSecurity/sysmon-config), but it is worth verifying. You can also use other repo, e.g. https://github.com/Neo23x0/sysmon-config, https://github.com/olafhartong/sysmon-modular. How to test detection? You can check powershell script from this site https://svch0st.medium.com/guide-to-named-pipes-and-hunting-for-cobalt-strike-pipes-dc46b2c5f575

Detection Logic

detection:
    selection:
        PipeName|startswith: '\PSHost'
    filter_main_generic:
        - Image|contains:
              - ':\Program Files\PowerShell\7-preview\pwsh.exe' # Powershell 7
              - ':\Program Files\PowerShell\7\pwsh.exe' # Powershell 7
              - ':\Windows\system32\dsac.exe'
              - ':\Windows\system32\inetsrv\w3wp.exe'   # this is sad :,( but it triggers FPs on Exchange servers
              - ':\Windows\System32\sdiagnhost.exe'
              - ':\Windows\system32\ServerManager.exe'
              - ':\Windows\system32\wbem\wmiprvse.exe'
              - ':\Windows\System32\WindowsPowerShell\v1.0\powershell_ise.exe'
              - ':\Windows\System32\WindowsPowerShell\v1.0\powershell.exe'
              - ':\Windows\System32\wsmprovhost.exe'
              - ':\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell_ise.exe'
              - ':\Windows\SysWOW64\WindowsPowerShell\v1.0\powershell.exe'
        - Image|contains|all:
              - 'C:\Program Files\WindowsApps\Microsoft.PowerShellPreview'
              - '\pwsh.exe'
        - Image|contains|all:
              - '\AppData\Local\Microsoft\WindowsApps\Microsoft.PowerShellPreview'
              - '\pwsh.exe'
    filter_optional_sqlserver: # Microsoft SQL Server\130\Tools\
        Image|startswith:
            - 'C:\Program Files (x86)\'
            - 'C:\Program Files\'
        Image|contains: '\Microsoft SQL Server\'
        Image|endswith: '\Tools\Binn\SQLPS.exe'
    filter_optional_azure_connected_machine_agent:
        # Azure Connected Machine Agent (https://devblogs.microsoft.com/powershell/azure-policy-guest-configuration-client/)
        Image|startswith: 'C:\Program Files\AzureConnectedMachineAgent\GCArcService'
        Image|endswith: '\GC\gc_worker.exe'
    filter_optional_citrix:
        Image|startswith: 'C:\Program Files\Citrix\'
    filter_optional_exchange:
        Image|startswith: 'C:\Program Files\Microsoft\Exchange Server\'
    filter_main_null:
        Image: null
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*