Windows Rundll32 Used to Start Cobalt Strike DLL Load via StartW

Alerts on rundll32.exe command lines that include a .dll and StartW function, consistent with Cobalt Strike DLL loading.

FreeReviewedSigma · High · v2

Product: windows
Category: process_creation
Author: Wojciech Lesicki (SigmaHQ), DRL 1.1
Published: 2021-06-01
Updated: 2026-07-31

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 identifies process creation where rundll32.exe is launched with command-line content indicating DLL loading through a StartW start function. Attackers can abuse signed Windows binaries like rundll32 to load malicious DLLs and stage execution while blending in with legitimate system behavior. The detection relies on Windows process creation telemetry, specifically Image/OriginalFileName and command-line strings that include rundll32 usage, a .dll reference, and StartW invocation.

Reporting behind it

Related detections9 linkedT1218.011 — drag to rearrange

Malicious DLL Execution With Non Standard Extension via rundll32

Andromeda Loader Execution via Rundll32 Desktop.ini Ordinal

Suspicious rundll32 Execution of sqlite3 DLL by Ordinal with TLB Argument

Malicious Zardoor Backdoor Execution via rundll32 (via process_creation)

Malicious Rundll32 Loading an Export From a User Path (via process_creation)

Renamed Regsvr32 or Rundll32 Loading a DLL With a Non-Standard Extension (via process_creation)

Malicious Rundll32 DllRegisterServer Execution From a User-Writable Path (via process_creation)

IMEEX Framework DLL Execution via Rundll32 Loading imaadp (via process_creation)

Suspicious Persistence via pcalua Launching rundll32 Control_RunDLL

Windows Rundll32 Used to Start Cobalt Strike DLL Load via StartW

Pivot detection · T1218.011 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-rundll32-exe-launching-dlls-via-cobalt-strike-startw-ae9c6a7c

title: Windows Rundll32 Used to Start Cobalt Strike DLL Load via StartW
id: 995d5841-f888-44c3-b5fd-4faec46a83a3
status: test
description: This rule identifies process creation where rundll32.exe is launched with command-line content indicating DLL loading through a StartW start function. Attackers can abuse signed Windows binaries like rundll32 to load malicious DLLs and stage execution while blending in with legitimate system behavior. The detection relies on Windows process creation telemetry, specifically Image/OriginalFileName and command-line strings that include rundll32 usage, a .dll reference, and StartW invocation.
references:
  - https://www.cobaltstrike.com/help-windows-executable
  - https://redcanary.com/threat-detection-report/
  - https://thedfirreport.com/2020/10/18/ryuk-in-5-hours/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_hktl_cobaltstrike_load_by_rundll32.yml
author: Wojciech Lesicki, Huntrule Team
date: 2021-06-01
modified: 2022-09-16
tags:
  - attack.stealth
  - attack.t1218.011
logsource:
  category: process_creation
  product: windows
detection:
  selection_rundll:
    - Image|endswith: \rundll32.exe
    - OriginalFileName: RUNDLL32.EXE
    - CommandLine|contains:
        - rundll32.exe
        - "rundll32 "
  selection_params:
    CommandLine|contains: .dll
    CommandLine|endswith:
      - " StartW"
      - ",StartW"
  condition: all of selection*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: ae9c6a7c-9521-42a6-915e-5aaa8689d529
    type: derived

Convert

This rule as a query you can run. Uses no unlock credit.

SplunkSPL