Detection: Windows PowerShell Script From WindowsApps Directory

Description

The following analytic identifies the execution of PowerShell scripts from the WindowsApps directory, which is a common technique used in malicious MSIX package execution. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process command lines and parent process paths. This activity is significant as adversaries have been observed using MSIX packages with embedded PowerShell scripts (particularly StartingScriptWrapper.ps1) to execute malicious code. 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_name="powershell.exe" AND (Processes.parent_process_path="*\\WindowsApps\\*" OR Processes.process="*WindowsApps*-file *" OR Processes.process="*WindowsApps*.ps1*") 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_powershell_script_from_windowsapps_directory_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

Annotations

Default Configuration

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

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 and command lines. 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 installed via the Microsoft Store or MSIX packages may execute PowerShell scripts from the WindowsApps directory as part of their normal operation. Verify if the MSIX package is from a trusted source and signed by a trusted publisher before taking action. Look for additional suspicious activities like network connections to unknown domains or execution of known malicious payloads.

Associated Analytic Story

• MSIX Package Abuse

• Malicious PowerShell

Risk Based Analytics (RBA)

Risk Message:

PowerShell script execution from WindowsApps directory detected on $dest$ by user $user$. This may indicate malicious MSIX package execution.

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://attack.mitre.org/techniques/T1059/001/

Detection Testing

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