detect_regasm_spawning_a_process.yml

name: Detect Regasm Spawning a Process
id: 72170ec5-f7d2-42f5-aefb-2b8be6aad15f
version: 5
date: '2024-08-14'
author: Michael Haag, Splunk
status: production
type: TTP
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.
data_source:
- Sysmon EventID 1
- Windows Event Log Security 4688
- CrowdStrike ProcessRollup2
search: '| 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 | `drop_dm_object_name(Processes)`
  | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)` | `detect_regasm_spawning_a_process_filter`'
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 regsvcs.exe
  may cause a false positive. Filter based endpoint usage, command line arguments,
  or process lineage.
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/
tags:
  analytic_story:
  - Suspicious Regsvcs Regasm Activity
  - Living Off The Land
  - DarkGate Malware
  - Snake Keylogger
  - Handala Wiper
  asset_type: Endpoint
  confidence: 80
  impact: 80
  message: An instance of $parent_process_name$ spawning $process_name$ was identified
    on endpoint $dest$ by user $user$ spawning a child process, typically not normal
    behavior for $parent_process_name$.
  mitre_attack_id:
  - T1218
  - T1218.009
  observable:
  - name: user
    type: User
    role:
    - Victim
  - name: dest
    type: Hostname
    role:
    - Victim
  - name: parent_process_name
    type: Process
    role:
    - Attacker
  - name: process_name
    type: Process
    role:
    - Attacker
  product:
  - Splunk Enterprise
  - Splunk Enterprise Security
  - Splunk Cloud
  required_fields:
  - _time
  - Processes.parent_process_name
  - Processes.dest
  - Processes.user
  - Processes.parent_process
  - Processes.process
  - Processes.process_id
  - Processes.parent_process_id
  risk_score: 64
  security_domain: endpoint
tests:
- name: True Positive Test
  attack_data:
  - data: 
      https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.009/atomic_red_team/windows-sysmon.log
    source: XmlWinEventLog:Microsoft-Windows-Sysmon/Operational
    sourcetype: xmlwineventlog