CmdID

CmdID / Rules / Windows

Execution of Suspicious File Type Extension

A Sigma rule for process creation on Windows, by Max Altgelt (Nextron Systems).

medium 1 program it names

What it looks for

its detection, as SigmaHQ writes it
detection:
  filter_main_deleted:
    Image|contains: ':\$Extend\$Deleted\'
  filter_main_driver_store:
    Image|contains: ':\Windows\System32\DriverStore\FileRepository\'
  filter_main_empty:
    Image:
      - '-'
      - ''
  filter_main_image:
    Image:
      - 'System'
      - 'Registry'
      - 'MemCompression'
      - 'vmmem'
  filter_main_msi_installers:
    Image|contains: ':\Windows\Installer\MSI'
  filter_main_msi_rollbackfiles:
    Image|contains: ':\Config.Msi\'
    Image|endswith:
      - '.rbf'
      - '.rbs'
  filter_main_null:
    Image: null
  filter_main_windows_temp:
    - ParentImage|contains: ':\Windows\Temp\'
    - Image|contains: ':\Windows\Temp\'
  filter_optional_avira:
    ParentImage|contains: ':\ProgramData\Avira\'
  filter_optional_docker:
    Image|endswith: 'com.docker.service'
    ParentImage: 'C:\Windows\System32\services.exe'
  filter_optional_firefox:
    Image|contains: ':\Program Files\Mozilla Firefox\'
  filter_optional_lzma_exe:
    Image|endswith: '\LZMA_EXE'
  filter_optional_myq_server:
    Image|endswith:
      - ':\Program Files (x86)\MyQ\Server\pcltool.dll'
      - ':\Program Files\MyQ\Server\pcltool.dll'
  filter_optional_nvidia:
    Image|contains: 'NVIDIA\NvBackend\'
    Image|endswith: '.dat'
  filter_optional_winpakpro:
    Image|contains:
      - ':\Program Files (x86)\WINPAKPRO\'
      - ':\Program Files\WINPAKPRO\'
    Image|endswith: '.ngn'
  filter_optional_wsl:
    Image|contains|all:
      - '\AppData\Local\Packages\'
      - '\LocalState\rootfs\'
  known_image_extension:
    Image|endswith:
      - '.bin'
      - '.cgi'
      - '.com'
      - '.exe'
      - '.scr'
      - '.tmp'
  condition: not known_image_extension and not 1 of filter_main_* and not 1 of filter_optional_*

The rule’s detection, its selections and fields in order of name. The whole rule, with its references and false positives, is on SigmaHQ, by Max Altgelt (Nextron Systems), under the Detection Rule License 1.1. CmdID evaluates it on a command line alone: a test on what a command line cannot show, such as the parent process or the user, is not met.

None of the everyday examples and documented commands on CmdID’s program pages trips it. To see whether a command line does, paste it into CmdID.

Programs and files it names

their pages here