Sigma Rule Library

Unsigned AppX Installation Attempt Using Add-AppxPackage - PsScript

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

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Detection logic

selection_cmdlet

ScriptBlockText|contains:
  - "Add-AppPackage "
  - "Add-AppxPackage "

selection_flag

ScriptBlockText|contains: " -AllowUnsigned"

Condition

all of selection_*

Raw YAML

title: Unsigned AppX Installation Attempt Using Add-AppxPackage - PsScript
id: 975b2262-9a49-439d-92a6-0709cccdf0b2
related:
    - id: 37651c2a-42cd-4a69-ae0d-22a4349aa04a
      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:
    product: windows
    category: ps_script
    definition: Script Block Logging must be enable
detection:
    selection_cmdlet:
        ScriptBlockText|contains:
            - 'Add-AppPackage '
            - 'Add-AppxPackage '
    selection_flag:
        ScriptBlockText|contains: ' -AllowUnsigned'
    condition: all of selection_*
falsepositives:
    - Installation of unsigned packages for testing purposes
level: medium

False positives

  • Installation of unsigned packages for testing purposes

References

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