Unsigned AppX Installation Attempt Using Add-AppxPackage

detection:
  selection_cmdlet:
    CommandLine|contains:
      - 'Add-AppPackage '
      - 'Add-AppxPackage '
  selection_flag:
    CommandLine|contains: ' -AllowUnsigned'
  selection_img:
    - Image|endswith:
        - '\powershell.exe'
        - '\pwsh.exe'
    - OriginalFileName:
        - 'PowerShell.EXE'
        - 'pwsh.dll'
  condition: all of selection_*

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 Nasreddine Bencherchali (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.