Windows MSIX Package Support Framework AI_STUBS Execution — Sigma Rule

Rule metadata and linked tags

Author: Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems). Source status: experimental; severity: low. Source dates: 2025-11-03 / not supplied.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: f83d8453e8576e833a514eafd32c728da52c8654c680b10ff2e0e0e3880a1b31

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Windows MSIX Package Support Framework AI_STUBS Execution
id: af5732ed-764e-489d-826d-0447c8b36242
status: experimental
description: |
    Detects execution of Advanced Installer MSIX Package Support Framework (PSF) components, specifically AI_STUBS executables with original filename 'popupwrapper.exe'.
    This activity may indicate malicious MSIX packages build with Advanced Installer leveraging the Package Support Framework to bypass application control restrictions.
references:
    - https://redcanary.com/blog/threat-intelligence/msix-installers/
    - https://redcanary.com/threat-detection-report/techniques/installer-packages/
    - https://learn.microsoft.com/en-us/windows/msix/package/package-support-framework
    - 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.execution
    - attack.stealth
    - attack.defense-impairment
    - attack.t1218
    - attack.t1553.005
    - attack.t1204.002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith:
            - '\AI_STUBS\AiStubX64Elevated.exe'
            - '\AI_STUBS\AiStubX86Elevated.exe'
            - '\AI_STUBS\AiStubX64.exe'
            - '\AI_STUBS\AiStubX86.exe'
        OriginalFileName: 'popupwrapper.exe'
    condition: selection
falsepositives:
    - Legitimate applications packaged with Advanced Installer using Package Support Framework
level: low

Original YAML and metadata in JSON

False positives

• Legitimate applications packaged with Advanced Installer using Package Support Framework

Source references

• https://redcanary.com/blog/threat-intelligence/msix-installers/
• https://redcanary.com/threat-detection-report/techniques/installer-packages/
• https://learn.microsoft.com/en-us/windows/msix/package/package-support-framework
• https://www.splunk.com/en_us/blog/security/msix-weaponization-threat-detection-splunk.html