Detection: Windows Advanced Installer MSIX with AI_STUBS Execution

Updated Date: 2025-08-05 ID: 56b2e58c-5909-49a3-998e-1f4815186ec2 Author: Michael Haag, Splunk Type: TTP Product: Splunk Enterprise Security

Description

The following analytic identifies the execution of Advanced Installer MSIX Package Support Framework (PSF) components, specifically the AI_STUBS executables with the original filename 'popupwrapper.exe'. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process paths and original filenames. This activity is significant as adversaries have been observed packaging malicious content within MSIX files built with Advanced Installer to bypass security controls. These AI_STUBS executables (with original filename 'popupwrapper.exe') are hallmark artifacts of potentially malicious MSIX packages. If confirmed malicious, this could allow attackers to execute arbitrary code, establish persistence, or deliver malware while evading traditional detection mechanisms.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime FROM datamodel=Endpoint.Processes where Processes.process_path IN ("*\\AI_STUBS\\AiStubX64Elevated.exe", "*\\AI_STUBS\\AiStubX86Elevated.exe", "*\\AI_STUBS\\AiStubX64.exe", "*\\AI_STUBS\\AiStubX86.exe") AND Processes.original_file_name="popupwrapper.exe" by Processes.action Processes.dest Processes.original_file_name Processes.parent_process Processes.parent_process_exec Processes.parent_process_guid Processes.parent_process_id Processes.parent_process_name Processes.parent_process_path Processes.process Processes.process_exec Processes.process_guid Processes.process_hash Processes.process_id Processes.process_integrity_level Processes.process_name Processes.process_path Processes.user Processes.user_id Processes.vendor_product 
3| `drop_dm_object_name("Processes")` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `windows_advanced_installer_msix_with_ai_stubs_execution_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	N/A	`'crowdstrike:events:sensor'`	`'crowdstrike'`
Sysmon EventID 1	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Microsoft-Windows-Sysmon/Operational'`
Windows Event Log Security 4688	Windows	`'XmlWinEventLog'`	`'XmlWinEventLog:Security'`

Macros Used

Name	Value
security_content_ctime	`convert timeformat="%Y-%m-%dT%H:%M:%S" ctime($field$)`
windows_advanced_installer_msix_with_ai_stubs_execution_filter	`search *`

windows_advanced_installer_msix_with_ai_stubs_execution_filter is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Annotations

- MITRE ATT&CK

+ Kill Chain Phases

+ NIST

+ CIS

- Threat Actors

ID	Technique	Tactic
T1218	System Binary Proxy Execution	Defense Evasion
T1553.005	Mark-of-the-Web Bypass	Defense Evasion
T1204.002	Malicious File	Execution

Exploitation

Installation

DE.CM

CIS 10

Default Configuration

This detection is configured by default in Splunk Enterprise Security to run with the following settings:

Setting	Value
Disabled	true
Cron Schedule	`0 * * * *`
Earliest Time	`-70m@m`
Latest Time	`-10m@m`
Schedule Window	`auto`
Creates Notable	Yes
Rule Title	`%name%`
Rule Description	`%description%`
Notable Event Fields	user, dest
Creates Risk Event	True

This configuration file applies to all detections of type TTP. These detections will use Risk Based Alerting and generate Notable Events.

Implementation

The detection is based on data that originates from Endpoint Detection and Response (EDR) agents. These agents are designed to provide security-related telemetry from the endpoints where the agent is installed. To implement this search, you must ingest logs that contain process execution information, including process paths. These logs must be processed using the appropriate Splunk Technology Add-ons that are specific to the EDR product. The logs must also be mapped to the Processes node of the Endpoint data model. Use the Splunk Common Information Model (CIM) to normalize the field names and speed up the data modeling process.

Known False Positives

Legitimate applications packaged with Advanced Installer using the Package Support Framework may trigger this detection. Verify if the MSIX package is from a trusted source and signed by a trusted publisher before taking action. Organizations that use Advanced Installer for legitimate software packaging may see false positives.

Associated Analytic Story

MSIX Package Abuse

Risk Based Analytics (RBA)

Risk Message:

Advanced Installer MSIX package with AI_STUBS execution detected on $dest$ by user $user$

Risk Object	Risk Object Type	Risk Score	Threat Objects
dest	system	60	process_path

References

Detection Testing

Test Type	Status	Dataset	Source	Sourcetype
Validation	✅ Passing	N/A	N/A	N/A
Unit	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`
Integration	✅ Passing	Dataset	`XmlWinEventLog:Microsoft-Windows-Sysmon/Operational`	`XmlWinEventLog`

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

Source: GitHub | Version: 1