Detection: Detect Regasm Spawning a Process

Description

The following analytic detects regasm.exe spawning a child process. This behavior is identified using data from Endpoint Detection and Response (EDR) agents, focusing on process creation events where regasm.exe is the parent process. This activity is significant because regasm.exe spawning a process is rare and can indicate an attempt to bypass application control mechanisms. If confirmed malicious, this could allow an attacker to execute arbitrary code, potentially leading to privilege escalation or persistent access within the environment. Immediate investigation is recommended to determine the legitimacy of the spawned process and any associated activities.

Search

1
2| tstats `security_content_summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where Processes.parent_process_name=regasm.exe NOT (Processes.process_name IN ("conhost.exe")) by Processes.dest Processes.user Processes.parent_process Processes.parent_process_name Processes.process_name Processes.process Processes.process_id Processes.parent_process_id 
3| `drop_dm_object_name(Processes)` 
4| `security_content_ctime(firstTime)` 
5| `security_content_ctime(lastTime)` 
6| `detect_regasm_spawning_a_process_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

Although unlikely, limited instances of regasm.exe or regsvcs.exe may cause a false positive. Filter based endpoint usage, command line arguments, or process lineage.

Associated Analytic Story

• Compromised Windows Host

• DarkGate Malware

• Handala Wiper

• Living Off The Land

• Snake Keylogger

• Suspicious Regsvcs Regasm Activity

Risk Based Analytics (RBA)

References

• https://attack.mitre.org/techniques/T1218/009/

• https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.009/T1218.009.md

• https://lolbas-project.github.io/lolbas/Binaries/Regsvcs/

• https://lolbas-project.github.io/lolbas/Binaries/Regasm/

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: 7