sigmamediumHunting

Unsigned AppX Installation Attempt Using Add-AppxPackage

Detects usage of the "Add-AppxPackage" or it's alias "Add-AppPackage" to install unsigned AppX packages

Detection Query

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

Author

Nasreddine Bencherchali (Nextron Systems)

Created

2023-01-31

Data Sources

windowsProcess Creation Events

Platforms

windows

References

Tags

attack.persistenceattack.stealth

Raw Content

title: Unsigned AppX Installation Attempt Using Add-AppxPackage
id: 37651c2a-42cd-4a69-ae0d-22a4349aa04a
related:
    - id: 975b2262-9a49-439d-92a6-0709cccdf0b2
      type: similar
    - id: 9a025188-6f2d-42f8-bb2f-d3a83d24a5af
      type: similar
status: test
description: Detects usage of the "Add-AppxPackage" or it's alias "Add-AppPackage" to install unsigned AppX packages
references:
    - https://learn.microsoft.com/en-us/windows/msix/package/unsigned-package
    - https://twitter.com/WindowsDocs/status/1620078135080325122
author: Nasreddine Bencherchali (Nextron Systems)
date: 2023-01-31
tags:
    - attack.persistence
    - attack.stealth
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith:
              - '\powershell.exe'
              - '\pwsh.exe'
        - OriginalFileName:
              - 'PowerShell.EXE'
              - 'pwsh.dll'
    selection_cmdlet:
        CommandLine|contains:
            - 'Add-AppPackage '
            - 'Add-AppxPackage '
    selection_flag:
        CommandLine|contains: ' -AllowUnsigned'
    condition: all of selection_*
falsepositives:
    - Installation of unsigned packages for testing purposes
level: medium