Windows Process Creation: Default-Argument Invocation of Rundll32/WerFault/Regsvcs/Regasm/Regsvr32

Alerts on suspicious Windows process launches of key binaries with missing/empty arguments, excluding common Edge/Chromium installer use.

FreeReviewedSigma · High · v1

Product: windows
Category: process_creation
Author: Oleg Kolesnikov @securonix invrep_de, oscd.community, Florian Roth (Nextron Systems), Christian Burkard (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2020-10-23
Updated: 2026-07-30

Analysis Detection

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1218.011Rundll32
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags Windows process executions where the Image and CommandLine end with specific binaries (rundll32.exe, WerFault.exe, regsvcs.exe, regasm.exe, or regsvr32.exe) without including additional command-line arguments. Attackers may rely on these “default” or improperly handled invocations as sacrificial processes to carry out capability injection or other stealthy actions without conforming to normal execution patterns. The detection relies on process creation telemetry that captures the executable path and full command line, with exclusions for certain EdgeUpdate/Chromium uninstall-related rundll32.exe activity.

Reporting behind it

Related detections9 linkedT1218.011 — drag to rearrange

Malicious Lunar Spider Loader Execution via rundll32 (via process_creation)

Malicious SYSTEM Persistence via Scheduled Task Running rundll32 at Startup (via process_creation)

Malicious Rundll32 Executing Image File as DLL

Suspicious Scheduled Task Executing Rundll32 DLL Export by Ordinal

Malicious Renamed Rundll32 Copied to Temp via Xcopy

Suspicious rundll32 Executing DLL from ProgramData (via process_creation)

Suspicious Rundll32 Loading DLL From Public or ProgramData Path via Process Creation (via process_creation)

Malicious LSASS Credential Dump via Rundll32 Comsvcs MiniDump via Process Creation (via process_creation)

Suspicious Rundll32 Execution Without a DLL Reference via Process Creation (via process_creation)

Windows Process Creation: Default-Argument Invocation of Rundll32/WerFault/Regsvcs/Regasm/Regsvr32

Pivot detection · T1218.011 · 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-creation-default-argument-invocation-of-rundll32-werfault-regsvc-a7c3d773

title: "Windows Process Creation: Default-Argument Invocation of Rundll32/WerFault/Regsvcs/Regasm/Regsvr32"
id: d969f74f-c1ac-4e5e-8a12-3e8cf1668db1
related:
  - id: f5647edc-a7bf-4737-ab50-ef8c60dc3add
    type: obsolete
  - id: a7c3d773-caef-227e-a7e7-c2f13c622329
    type: derived
status: test
description: This rule flags Windows process executions where the Image and CommandLine end with specific binaries (rundll32.exe, WerFault.exe, regsvcs.exe, regasm.exe, or regsvr32.exe) without including additional command-line arguments. Attackers may rely on these “default” or improperly handled invocations as sacrificial processes to carry out capability injection or other stealthy actions without conforming to normal execution patterns. The detection relies on process creation telemetry that captures the executable path and full command line, with exclusions for certain EdgeUpdate/Chromium uninstall-related rundll32.exe activity.
references:
  - https://blog.malwarebytes.com/malwarebytes-news/2020/10/kraken-attack-abuses-wer-service/
  - https://www.cobaltstrike.com/help-opsec
  - https://twitter.com/CyberRaiju/status/1251492025678983169
  - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/regsvr32
  - https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/rundll32
  - https://learn.microsoft.com/en-us/dotnet/framework/tools/regasm-exe-assembly-registration-tool
  - https://learn.microsoft.com/en-us/dotnet/framework/tools/regsvcs-exe-net-services-installation-tool
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_susp_bad_opsec_sacrificial_processes.yml
author: Oleg Kolesnikov @securonix invrep_de, oscd.community, Florian Roth (Nextron Systems), Christian Burkard (Nextron Systems), Huntrule Team
date: 2020-10-23
modified: 2024-08-15
tags:
  - attack.stealth
  - attack.t1218.011
logsource:
  category: process_creation
  product: windows
detection:
  selection_werfault:
    Image|endswith: \WerFault.exe
    CommandLine|endswith: WerFault.exe
  selection_rundll32:
    Image|endswith: \rundll32.exe
    CommandLine|endswith: rundll32.exe
  selection_regsvcs:
    Image|endswith: \regsvcs.exe
    CommandLine|endswith: regsvcs.exe
  selection_regasm:
    Image|endswith: \regasm.exe
    CommandLine|endswith: regasm.exe
  selection_regsvr32:
    Image|endswith: \regsvr32.exe
    CommandLine|endswith: regsvr32.exe
  filter_optional_edge_update:
    ParentImage|contains: \AppData\Local\Microsoft\EdgeUpdate\Install\{
    Image|endswith: \rundll32.exe
    CommandLine|endswith: rundll32.exe
  filter_optional_chromium_installer:
    ParentImage|contains:
      - \AppData\Local\BraveSoftware\Brave-Browser\Application\
      - \AppData\Local\Google\Chrome\Application\
    ParentImage|endswith: \Installer\setup.exe
    ParentCommandLine|contains: "--uninstall "
    Image|endswith: \rundll32.exe
    CommandLine|endswith: rundll32.exe
  condition: 1 of selection_* and not 1 of filter_optional_*
falsepositives:
  - Unlikely
level: high
license: DRL-1.1

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