Windows Process Execution of Regasm/Regsvcs from Uncommon Directories

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1218.009Regsvcs/Regasm
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process creations where Regasm.exe or Regsvcs.exe is executed from specific, potentially suspicious directory paths (e.g., Temp, Startup, PerfLogs, Users\Public, and Windows Temp). Attackers may use these Windows registration utilities to execute or stage components in a way that blends into normal system behavior. It relies on Windows process creation telemetry containing the image name and the full command line for directory/path context.

Reporting behind it

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Suspicious PowerShell Spawning .NET LOLBIN (via process_creation)

RegAsm.exe Process Execution Missing Command-Line and Assembly Path (Windows)

Windows RegAsm.exe Initiates Network Connection to Public IP

Windows Process Execution of Regasm/Regsvcs from Uncommon Directories

Pivot detection · T1218.009 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-process-execution-of-regasm-regsvcs-from-uncommon-directories-cc368ed0

title: Windows Process Execution of Regasm/Regsvcs from Uncommon Directories
id: 2ca73eca-854d-4869-930f-7ff5e098e545
related:
  - id: e9f8f8cc-07cc-4e81-b724-f387db9175e4
    type: derived
  - id: cc368ed0-2411-45dc-a222-510ace303cb2
    type: derived
status: test
description: This rule flags process creations where Regasm.exe or Regsvcs.exe is executed from specific, potentially suspicious directory paths (e.g., Temp, Startup, PerfLogs, Users\Public, and Windows Temp). Attackers may use these Windows registration utilities to execute or stage components in a way that blends into normal system behavior. It relies on Windows process creation telemetry containing the image name and the full command line for directory/path context.
references:
  - https://www.fortiguard.com/threat-signal-report/4718?s=09
  - https://lolbas-project.github.io/lolbas/Binaries/Regasm/
  - https://lolbas-project.github.io/lolbas/Binaries/Regsvcs/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_regasm_regsvcs_uncommon_location_execution.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 2022-08-25
modified: 2023-02-13
tags:
  - attack.stealth
  - attack.t1218.009
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith:
        - \Regsvcs.exe
        - \Regasm.exe
    - OriginalFileName:
        - RegSvcs.exe
        - RegAsm.exe
  selection_dir:
    CommandLine|contains:
      - \AppData\Local\Temp\
      - \Microsoft\Windows\Start Menu\Programs\Startup\
      - \PerfLogs\
      - \Users\Public\
      - \Windows\Temp\
  condition: all of selection_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1

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