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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.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Endpoint
  • Last Updated: 2024-08-14
  • Author: Michael Haag, Splunk
  • ID: c3bc1430-04e7-4178-835f-047d8e6e97df

Annotations

ATT&CK

ATT&CK

ID Technique Tactic
T1218 System Binary Proxy Execution Defense Evasion
T1218.009 Regsvcs/Regasm Defense Evasion
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 10
CVE 


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| 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 
| `drop_dm_object_name(Processes)` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| regex process="(?i)(regasm\.exe.{0,4}$)" 
| `detect_regasm_with_no_command_line_arguments_filter`

Macros

The SPL above uses the following Macros:

:information_source: detect_regasm_with_no_command_line_arguments_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required fields

List of fields required to use this analytic.

  • _time
  • Processes.dest
  • Processes.user
  • Processes.parent_process_name
  • Processes.parent_process
  • Processes.original_file_name
  • Processes.process_name
  • Processes.process
  • Processes.process_id
  • Processes.parent_process_path
  • Processes.process_path
  • Processes.parent_process_id

How To Implement

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

RBA

Risk Score Impact Confidence Message
49.0 70 70 The process $process_name$ was spawned by $parent_process_name$ without any command-line arguments on $dest$ by $user$.

:information_source: The Risk Score is calculated by the following formula: Risk Score = (Impact * Confidence/100). Initial Confidence and Impact is set by the analytic author.

Reference

Test Dataset

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 | version: 5