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Windows AppX Deployment Unsigned Package Installation

Detects attempts to install unsigned MSIX/AppX packages using the -AllowUnsigned parameter via AppXDeployment-Server events

MITRE ATT&CK

T1204.002 T1553.005

defense-evasionexecution

Detection Query

selection:
  EventID: 603
  Flags: "8388608"
condition: selection

Author

Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems)

Created

2025-11-03

Data Sources

windowsappxdeployment-server

Platforms

windows

References

Tags

attack.defense-evasionattack.executionattack.t1204.002attack.t1553.005

Raw Content

title: Windows AppX Deployment Unsigned Package Installation
id: 9a025188-6f2d-42f8-bb2f-d3a83d24a5af
related:
    - id: 37651c2a-42cd-4a69-ae0d-22a4349aa04a
      type: similar
    - id: 975b2262-9a49-439d-92a6-0709cccdf0b2
      type: similar
status: experimental
description: Detects attempts to install unsigned MSIX/AppX packages using the -AllowUnsigned parameter via AppXDeployment-Server events
references:
    - https://docs.microsoft.com/en-us/powershell/module/appx/add-appxpackage
    - https://www.splunk.com/en_us/blog/security/msix-weaponization-threat-detection-splunk.html
author: Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-11-03
tags:
    - attack.defense-evasion
    - attack.execution
    - attack.t1204.002
    - attack.t1553.005
logsource:
    product: windows
    service: appxdeployment-server
detection:
    selection:
        EventID: 603
        Flags: '8388608'
    condition: selection
falsepositives:
    - Legitimate installation of unsigned packages for legitimate purposes such as development or testing
level: medium