Windows Suspicious Execution of Regasm/Regsvcs With Uncommon Command-Line Extension
Flags Regasm.exe/Regsvcs.exe runs that include unusual extensions in the command line, which may indicate stealthy misuse.
- Product
- windows
- Category
- process_creation
- Author
- Nasreddine Bencherchali (Nextron Systems) (SigmaHQ), DRL 1.1
- Published
- 2023-02-13
- Updated
- 2026-07-30
ATT&CK techniques
Defense EvasionRecon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact
What it detects
This rule flags process creation events where Regasm.exe or Regsvcs.exe is executed and the command line contains an uncommon file extension (e.g., .dat, .gif, .jpeg, .jpg, .png, .txt). Attackers may use these Windows utilities to register or manipulate components while disguising activity via atypical extension arguments. It relies on Windows process creation telemetry including the executed image path and the full command line.
Reporting behind it
- fortiguard.comhttps://www.fortiguard.com/threat-signal-report/4718?s=09
- lolbas-project.github.iohttps://lolbas-project.github.io/lolbas/Binaries/Regasm/
- lolbas-project.github.iohttps://lolbas-project.github.io/lolbas/Binaries/Regsvcs/
- github.comhttps://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_regasm_regsvcs_uncommon_extension_execution.yml
Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.
title: Windows Suspicious Execution of Regasm/Regsvcs With Uncommon Command-Line Extension
id: a92be7ac-019f-47e4-aac7-3ccf3e04d470
related:
- id: cc368ed0-2411-45dc-a222-510ace303cb2
type: derived
- id: e9f8f8cc-07cc-4e81-b724-f387db9175e4
type: derived
status: test
description: This rule flags process creation events where Regasm.exe or Regsvcs.exe is executed and the command line contains an uncommon file extension (e.g., .dat, .gif, .jpeg, .jpg, .png, .txt). Attackers may use these Windows utilities to register or manipulate components while disguising activity via atypical extension arguments. It relies on Windows process creation telemetry including the executed image path and the full command line.
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_extension_execution.yml
author: Nasreddine Bencherchali (Nextron Systems), Huntrule Team
date: 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_extension:
CommandLine|contains:
- .dat
- .gif
- .jpeg
- .jpg
- .png
- .txt
condition: all of selection_*
falsepositives:
- Unknown
level: medium
license: DRL-1.1