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Detection rules › Sigma

Windows MSIX Package Support Framework AI_STUBS Execution

Status
experimental
Severity
low
Log source
product windows, category process_creation
Author
Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems)
Source
github.com/SigmaHQ/sigma

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.

MITRE ATT&CK coverage

TacticTechniques
ExecutionT1204.002 User Execution: Malicious File
StealthT1218 System Binary Proxy Execution
Defense ImpairmentT1553.005 Subvert Trust Controls: Mark-of-the-Web Bypass

Event coverage

ProviderEventTitle
SysmonEvent ID 1Process creation

Rule body yaml

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

Stages and Predicates

Stage 0: condition

selection

Stage 1: selection

selection:
    Image|endswith:
        - '\AI_STUBS\AiStubX64Elevated.exe'
        - '\AI_STUBS\AiStubX86Elevated.exe'
        - '\AI_STUBS\AiStubX64.exe'
        - '\AI_STUBS\AiStubX86.exe'
    OriginalFileName: 'popupwrapper.exe'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

FieldKindValues
Imageends_with
  • \AI_STUBS\AiStubX64.exe
  • \AI_STUBS\AiStubX64Elevated.exe
  • \AI_STUBS\AiStubX86.exe
  • \AI_STUBS\AiStubX86Elevated.exe
OriginalFileNameeq
  • popupwrapper.exe corpus 2 (sigma 1, splunk 1)