Windows MSIX Package Support Framework AI_STUBS Execution

Severity: low
Author: Michael Haag, Swachchhanda Shrawan Poudel (Nextron Systems)
Source: upstream

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

Tactic	Techniques
Execution	`T1204.002` User Execution: Malicious File
Defense Evasion	`T1218` System Binary Proxy Execution, `T1553.005` Subvert Trust Controls: Mark-of-the-Web Bypass

Event coverage

Provider	Event ID	Title
Sysmon	1	Process creation

Stages and Predicates

Stage 1: `selection`

or:
Image|endswith: '\AI_STUBS\AiStubX64.exe'
Image|endswith: '\AI_STUBS\AiStubX64Elevated.exe'
Image|endswith: '\AI_STUBS\AiStubX86.exe'
Image|endswith: '\AI_STUBS\AiStubX86Elevated.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.