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 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 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

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