Windows PowerShell MSIX Package Installation
The following analytic detects the execution of PowerShell commands to install unsigned AppX packages using Add-AppxPackage or Add-AppPackage cmdlets with the -AllowUnsigned flag. This detection leverages PowerShell…
Description
The following analytic detects the execution of PowerShell commands to install unsigned AppX packages using Add-AppxPackage or Add-AppPackage cmdlets with the -AllowUnsigned flag. This detection leverages PowerShell Script Block Logging (EventCode=4104) to capture the full command content. This activity is significant as adversaries may use unsigned AppX packages to install malicious applications, bypass security controls, or establish persistence. If confirmed malicious, this could allow attackers to install unauthorized applications that may contain malware, backdoors, or other malicious components.
Detection logic
Detection requirements
- Platform
- Windows
The rule states no platform. This is derived from the 2 ATT&CK techniques it maps to.
- Log source category
- powershell_script_block_logging_4104
Known benign triggers
- Installation of unsigned packages for testing purposes by developers or system administrators. Legitimate software development and testing activities may trigger this detection. Internal application development teams testing MSIX packages before signing. System administrators installing custom unsigned applications for business purposes. Note: The -AllowUnsigned flag is only available on Windows 11 and later versions.
MITRE ATT&CK mappings
0 exclusive techniques.This is coverage no other published rule has; it is not this rule's total technique count.
References
| Reference | Cited by |
|---|---|
| attack.mitre.org/techniques/T1059/001/ | 6 |
| attack.mitre.org/techniques/T1547/001/ | Only this detection cites it |
| learn.microsoft.com/en-us/powershell/module/appx/add-appxpackage | 2 |
| learn.microsoft.com/en-us/powershell/module/appx/add-appxpackage?view=windowsserver2025-ps | Only this detection cites it |
| learn.microsoft.com/en-us/windows/msix/desktop/powershell-msix-cmdlets | Only this detection cites it |
| learn.microsoft.com/en-us/windows/msix/package/unsigned-package | 4from 2 sources |
| twitter.com/WindowsDocs/status/1620078135080325122 | 3from 2 sources |
From the source
- At source
- Open at source
- Upstream identifier
- d2f77901-dbfa-42d9-8af7-dcd0f1a50a2f
- Tagged by the source as
- Malicious PowerShellMSIX Package AbuseEndpointendpointSplunk CloudSplunk EnterpriseSplunk Enterprise Securityendpoint
Licence
- Published under
- Apache License 2.0Read the licence
- Attribution
- Required
- Obtained under
- Apache-2.0Read the origin licence
Authorship
- Written by
- Published
- Aug 26, 2026
- Version
- 1