Detection: Windows Explorer.exe Spawning PowerShell or Cmd

Description

This detection identifies instances where Windows Explorer.exe spawns PowerShell or cmd.exe processes, particularly focusing on executions initiated by LNK files. This behavior is associated with the ZDI-CAN-25373 Windows shortcut zero-day vulnerability, where specially crafted LNK files are used to trigger malicious code execution through cmd.exe or powershell.exe. This technique has been actively exploited by multiple APT groups in targeted attacks through both HTTP and SMB delivery methods.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_path="*\\explorer.exe" `process_powershell` OR `process_cmd`  by  Processes.dest Processes.process_current_directory Processes.process_path Processes.process Processes.original_file_name Processes.parent_process Processes.parent_process_name Processes.parent_process_path Processes.parent_process_guid Processes.parent_process_id Processes.process_guid Processes.process_id Processes.user 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)` 
6| `windows_explorer_exe_spawning_powershell_or_cmd_filter`

Data Source

Name	Platform	Sourcetype	Source
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 user actions may trigger Explorer.exe to spawn PowerShell or cmd.exe, such as right-clicking and selecting "Open PowerShell window here" or similar options. Filter as needed based on your environment's normal behavior patterns.

Associated Analytic Story

• ZDI-CAN-25373 Windows Shortcut Exploit Abused as Zero-Day

References

• https://www.zerodayinitiative.com/advisories/ZDI-CAN-25373/

• https://www.trendmicro.com/en_us/research/25/c/windows-shortcut-zero-day-exploit.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