Detection: Windows Get-Variable.EXE Execution from WindowsApps Folder

Description

An attacker can obtain persistence by hijacking the PowerShell cmdlet 'Get-Variable' by placing Get-Variable.exe in the WindowsApps folder, which is part of the PowerShell path. Whenever a PowerShell window is opened via a scheduled task, the malicious Get-Variable.exe will be run. This activity was first associated with the Colibri malware.

Search

 1
 2| tstats `security_content_summariesonly`
 3  count min(_time) as firstTime
 4        max(_time) as lastTime
 5
 6from datamodel=Endpoint.Processes where
 7
 8Processes.process_path="*\\AppData\\Local\\Microsoft\\WindowsApps\\Get-Variable.exe"
 9
10by Processes.process Processes.vendor_product Processes.user_id Processes.process_hash
11   Processes.parent_process_name Processes.parent_process_exec Processes.action
12   Processes.dest Processes.process_current_directory Processes.process_path
13   Processes.process_integrity_level Processes.original_file_name Processes.parent_process
14   Processes.parent_process_path Processes.parent_process_guid Processes.parent_process_id
15   Processes.process_guid Processes.process_id Processes.user Processes.process_name
16
17
18| `drop_dm_object_name(Processes)`
19
20| `security_content_ctime(firstTime)`
21
22| `security_content_ctime(lastTime)`
23
24| `windows_get_variable_exe_execution_from_windowsapps_folder_filter`

Data Source

Name	Platform	Sourcetype	Source
CrowdStrike ProcessRollup2	Other	'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 the process GUID, process name, and parent process. Additionally, you must ingest complete command-line executions. 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

Some legitimate administrative tools may use custom executables in the WindowsApps folder for persistence or automation. Verify the executable's origin before flagging to avoid false positives.

Associated Analytic Story

• Windows Persistence Techniques

Risk Based Analytics (RBA)

Risk Message:

Potential Persistence with Get-Variable.exe from WindowsApps Folder activity observed on $dest$.

References

• https://thehackernews.com/2022/04/researchers-uncover-how-colibri-malware.html

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