name: Detect Regasm Spawning a Process
id: 72170ec5-f7d2-42f5-aefb-2b8be6aad15f
version: 1
date: '2021-02-12'
author: Michael Haag, Splunk
type: batch
datamodel:
- Endpoint
description: The following analytic identifies regasm.exe spawning a process. This
  particular technique has been used in the wild to bypass application control products.
  Regasm.exe and Regsvcs.exe are signed by Microsoft. Spawning of a child process
  is rare from either process and should be investigated further. During investigation,
  identify and retrieve the content being loaded. Review parallel processes for additional
  suspicious behavior. Gather any other file modifications and review accordingly.
  regsvcs.exe and regasm.exe are natively found in C:\Windows\Microsoft.NET\Framework\v*\regasm|regsvcs.exe
  and C:\Windows\Microsoft.NET\Framework64\v*\regasm|regsvcs.exe.
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
  by Processes.dest Processes.user Processes.parent_process 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: To successfully implement this search you need to be ingesting information
  on process that include the name of the process responsible for the changes from
  your endpoints into the `Endpoint` datamodel in the `Processes` node.
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
  asset_type: Endpoint
  automated_detection_testing: passed
  cis20:
  - CIS 8
  dataset:
  - https://media.githubusercontent.com/media/splunk/attack_data/master/datasets/attack_techniques/T1218.009/atomic_red_team/windows-sysmon.log
  kill_chain_phases:
  - Actions on Objectives
  mitre_attack_id:
  - T1218.009
  nist:
  - PR.PT
  - DE.CM
  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
  security_domain: endpoint
