Rundll32.exe DLL Export Calls by Ordinal (Windows Process Creation)

Detects rundll32.exe commands that specify DLL exports by ordinal using “.dll #” syntax.

FreeReviewedSigma · Medium · v5

Product: windows
Category: process_creation
Author: Florian Roth (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2019-10-22
Updated: 2026-07-31

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 events where rundll32.exe loads a DLL export using an ordinal notation (e.g., strings containing ',#' and '.dll #' or '.ocx #'). Using ordinal-based export calls can obscure intent and is a common technique in stealthy execution chains. It relies on Windows process creation telemetry, matching the Image/OriginalFileName for rundll32.exe and specific patterns in the CommandLine. Optional exclusions reduce matches for known benign tooling patterns.

Reporting behind it

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Rundll32.exe DLL Export Calls by Ordinal (Windows Process Creation)

Pivot detection · T1218.011 · 9 related

Changelog

v5
Candidate ingested via manual entry.2026-07-31
v4
Candidate ingested via manual entry.2026-07-31
v3
Candidate ingested via manual entry.2026-07-31
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-loads-dll-exports-by-ordinal-in-command-line-e79a9e79

title: Rundll32.exe DLL Export Calls by Ordinal (Windows Process Creation)
id: cfa15580-4c53-4cdd-a83a-43ec8652545e
status: stable
description: "This rule identifies process creation events where rundll32.exe loads a DLL export using an ordinal notation (e.g., strings containing ',#' and '.dll #' or '.ocx #'). Using ordinal-based export calls can obscure intent and is a common technique in stealthy execution chains. It relies on Windows process creation telemetry, matching the Image/OriginalFileName for rundll32.exe and specific patterns in the CommandLine. Optional exclusions reduce matches for known benign tooling patterns."
references:
  - https://web.archive.org/web/20200530031906/https://techtalk.pcmatic.com/2017/11/30/running-dll-files-malware-analysis/
  - https://github.com/Neo23x0/DLLRunner
  - https://twitter.com/cyb3rops/status/1186631731543236608
  - https://www.welivesecurity.com/2022/03/01/isaacwiper-hermeticwizard-wiper-worm-targeting-ukraine/
  - https://github.com/SigmaHQ/sigma/blob/master/rules-threat-hunting/windows/process_creation/proc_creation_win_rundll32_by_ordinal.yml
author: Florian Roth (Nextron Systems), Huntrule Team
date: 2019-10-22
modified: 2024-07-16
tags:
  - attack.stealth
  - attack.t1218.011
  - detection.threat-hunting
logsource:
  category: process_creation
  product: windows
detection:
  selection_img:
    - Image|endswith: \rundll32.exe
    - OriginalFileName: RUNDLL32.EXE
  selection_cli:
    CommandLine|contains:
      - ",#"
      - ", #"
      - ".dll #"
      - ".ocx #"
  filter_optional_edge:
    CommandLine|contains|all:
      - EDGEHTML.dll
      - "#141"
  filter_optional_vsbuild_dll:
    ParentImage|contains:
      - \Msbuild\Current\Bin\
      - \VC\Tools\MSVC\
      - \Tracker.exe
    CommandLine|contains:
      - \FileTracker32.dll,#1
      - \FileTracker32.dll",#1
      - \FileTracker64.dll,#1
      - \FileTracker64.dll",#1
  condition: all of selection_* and not 1 of filter_optional_*
falsepositives:
  - False positives depend on scripts and administrative tools used in the monitored environment.
  - Windows control panel elements have been identified as source (mmc).
level: medium
license: DRL-1.1
related:
  - id: e79a9e79-eb72-4e78-a628-0e7e8f59e89c
    type: derived

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