ID | Technique | Tactic |
---|---|---|
T1218 | System Binary Proxy Execution | Defense Evasion |
T1218.009 | Regsvcs/Regasm | Defense Evasion |
Detection: Detect Regasm with no Command Line Arguments
Description
The following analytic detects instances of regasm.exe running without command line arguments. This behavior typically indicates process injection, where another process manipulates regasm.exe. The detection leverages Endpoint Detection and Response (EDR) data, focusing on process names and command-line executions. This activity is significant as it may signal an attempt to evade detection or execute malicious code. If confirmed malicious, attackers could achieve code execution, potentially leading to privilege escalation, persistence, or access to sensitive information. Investigate network connections, parallel processes, and suspicious module loads for further context.
Search
1
2| tstats `security_content_summariesonly` count FROM datamodel=Endpoint.Processes where `process_regasm` by _time span=1h Processes.process_id Processes.process_name Processes.dest Processes.user Processes.process_path Processes.process Processes.parent_process_name
3| `drop_dm_object_name(Processes)`
4| `security_content_ctime(firstTime)`
5| `security_content_ctime(lastTime)`
6| regex process="(?i)(regasm\.exe.{0,4}$)"
7| `detect_regasm_with_no_command_line_arguments_filter`
Data Source
Name | Platform | Sourcetype | Source | Supported App |
---|---|---|---|---|
CrowdStrike ProcessRollup2 | N/A | 'crowdstrike:events:sensor' |
'crowdstrike' |
N/A |
Macros Used
Name | Value |
---|---|
process_regasm | (Processes.process_name=regasm.exe OR Processes.original_file_name=RegAsm.exe) |
detect_regasm_with_no_command_line_arguments_filter | search * |
detect_regasm_with_no_command_line_arguments_filter
is an empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.
Annotations
Default Configuration
This detection is configured by default in Splunk Enterprise Security to run with the following settings:
Setting | Value |
---|---|
Disabled | true |
Cron Schedule | 0 * * * * |
Earliest Time | -70m@m |
Latest Time | -10m@m |
Schedule Window | auto |
Creates Notable | Yes |
Rule Title | %name% |
Rule Description | %description% |
Notable Event Fields | user, dest |
Creates Risk Event | True |
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 may cause a false positive. Filter based endpoint usage, command line arguments, or process lineage.
Associated Analytic Story
Risk Based Analytics (RBA)
Risk Message | Risk Score | Impact | Confidence |
---|---|---|---|
The process $process_name$ was spawned by $parent_process_name$ without any command-line arguments on $dest$ by $user$. | 49 | 70 | 70 |
References
Detection Testing
Test Type | Status | Dataset | Source | Sourcetype |
---|---|---|---|---|
Validation | ✅ Passing | N/A | N/A | N/A |
Unit | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
Integration | ✅ Passing | Dataset | XmlWinEventLog:Microsoft-Windows-Sysmon/Operational |
xmlwineventlog |
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: 5