Detection: Rundll32 Control RunDLL Hunt

Description

The following analytic identifies instances of rundll32.exe executing with Control_RunDLL in the command line, which is indicative of loading a .cpl or other file types. This detection leverages data from Endpoint Detection and Response (EDR) agents, focusing on process execution logs and command-line arguments. This activity is significant as rundll32.exe can be exploited to execute malicious Control Panel Item files, potentially linked to CVE-2021-40444. If confirmed malicious, this could allow attackers to execute arbitrary code, escalate privileges, or maintain persistence within the environment.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_rundll32` Processes.process=*Control_RunDLL*  by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id Processes.original_file_name 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `rundll32_control_rundll_hunt_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 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

This is a hunting detection, meant to provide a understanding of how voluminous control_rundll is within the environment.

Associated Analytic Story

• Living Off The Land

• Microsoft MSHTML Remote Code Execution CVE-2021-40444

• Suspicious Rundll32 Activity

Risk Based Analytics (RBA)

References

• https://strontic.github.io/xcyclopedia/library/rundll32.exe-111474C61232202B5B588D2B512CBB25.html

• https://app.any.run/tasks/36c14029-9df8-439c-bba0-45f2643b0c70/

• https://attack.mitre.org/techniques/T1218/011/

• https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-40444

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.002/T1218.002.yaml

• https://redcanary.com/blog/intelligence-insights-december-2021/

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: 4