Detection: Regsvr32 Silent and Install Param Dll Loading

Description

The following analytic detects the loading of a DLL using the regsvr32 application with the silent parameter and DLLInstall execution. It leverages data from Endpoint Detection and Response (EDR) agents, focusing on process command-line arguments and parent process details. This activity is significant as it is commonly used by RAT malware like Remcos and njRAT to load malicious DLLs on compromised machines. If confirmed malicious, this technique could allow attackers to execute arbitrary code, maintain persistence, and further compromise the system.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where `process_regsvr32` AND Processes.process="*/i*" by Processes.dest Processes.parent_process Processes.process Processes.parent_process_name Processes.process_name Processes.original_file_name Processes.user 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| where match(process,"(?i)[\-
7|\/][Ss]{1}") 
8| `regsvr32_silent_and_install_param_dll_loading_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

Other third part application may used this parameter but not so common in base windows environment.

Associated Analytic Story

• AsyncRAT

• Data Destruction

• Hermetic Wiper

• Living Off The Land

• Remcos

• Suspicious Regsvr32 Activity

Risk Based Analytics (RBA)

References

• https://app.any.run/tasks/dc93ee63-050c-4ff8-b07e-8277af9ab939/

• https://attack.mitre.org/techniques/T1218/010/

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