Windows rundll32.exe Started Without Command-Line Parameters

Alerts on Windows process launches of rundll32.exe with no parameters, excluding likely benign parent paths.

FreeUnreviewedSigmahighv1

windows-rundll32-exe-started-without-command-line-parameters-1775e15e

title: Windows rundll32.exe Started Without Command-Line Parameters
id: 39107785-8521-4332-815c-21d3d804fdc1
status: test
description: This rule flags process creation events where rundll32.exe is launched with no command-line parameters beyond the executable name. Attackers may use rundll32 as a stealthy execution primitive, and starting it without parameters can indicate suspicious staging or beacon-related behavior. The detection relies on Windows process creation telemetry, specifically matching the CommandLine endings and excluding common parent process paths under user AppData and Microsoft Edge directories.
references:
  - https://www.cobaltstrike.com/help-opsec
  - https://twitter.com/ber_m1ng/status/1397948048135778309
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_rundll32_no_params.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2021-05-27
modified: 2023-08-31
tags:
  - attack.stealth
  - attack.t1202
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    CommandLine|endswith:
      - \rundll32.exe
      - \rundll32.exe"
      - \rundll32
  filter:
    ParentImage|contains:
      - \AppData\Local\
      - \Microsoft\Edge\
  condition: selection and not filter
falsepositives:
  - Possible but rare
level: high
license: DRL-1.1
related:
  - id: 1775e15e-b61b-4d14-a1a3-80981298085a
    type: derived

What it detects

This rule flags process creation events where rundll32.exe is launched with no command-line parameters beyond the executable name. Attackers may use rundll32 as a stealthy execution primitive, and starting it without parameters can indicate suspicious staging or beacon-related behavior. The detection relies on Windows process creation telemetry, specifically matching the CommandLine endings and excluding common parent process paths under user AppData and Microsoft Edge directories.

Known false positives

Possible but rare

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