Windows: CLR DLL Loaded by Office Applications

Alerts when Excel, Word, Outlook, PowerPoint, Publisher, or OneNote loads clr.dll on Windows.

FreeReviewedSigma · Medium · v2

Product: windows
Category: image_load
Author: Antonlovesdnb (SigmaHQ), DRL 1.1
Published: 2020-02-19
Updated: 2026-07-31

ATT&CK techniques

Execution

Recon
Resource Dev
Initial Access
Execution
- T1204.002Malicious File
Persistence
Priv Esc
Defense Evasion
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags executions where an Office application loads clr.dll, indicating the .NET Common Language Runtime being brought into an Office process. Adversaries may use this behavior to execute managed code within a trusted Office context. It relies on image load telemetry that records the host process image name and the DLL path loaded, specifically detecting clr.dll being loaded by excel.exe, mspub.exe, outlook.exe, onenote.exe, onenoteim.exe, powerpnt.exe, or winword.exe.

Reporting behind it

Related detections9 linkedT1204.002 — drag to rearrange

Suspicious OneNote Spawning Script Interpreter (via process_creation)

Suspicious vbc.exe Spawned by Installer Process

Suspicious n8n Campaign RMM Installer Masquerading as OneDrive Document

Suspicious NFe-Themed Brazilian Lure Executable Execution

Suspicious Executable Dropped in Public Users Directory Named Ctrlpanel (via file_event)

Suspicious Interlock Fake Updater Executable Execution

Malicious Office Application Loading a User-Path DLL via Regsvr32 or Rundll32 (via process_creation)

Suspicious Program Execution From a Mounted ISO or Disk Image (via process_creation)

SocGholish Fake Browser Update Script Execution (via process_creation)

Windows: CLR DLL Loaded by Office Applications

Pivot detection · T1204.002 · 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-clr-dll-loaded-by-microsoft-office-applications-d13c43f0

title: "Windows: CLR DLL Loaded by Office Applications"
id: 5f7b2557-5c23-41bc-82e0-6f6b6d6e52f4
status: test
description: This rule flags executions where an Office application loads clr.dll, indicating the .NET Common Language Runtime being brought into an Office process. Adversaries may use this behavior to execute managed code within a trusted Office context. It relies on image load telemetry that records the host process image name and the DLL path loaded, specifically detecting clr.dll being loaded by excel.exe, mspub.exe, outlook.exe, onenote.exe, onenoteim.exe, powerpnt.exe, or winword.exe.
references:
  - https://medium.com/threatpunter/detecting-adversary-tradecraft-with-image-load-event-logging-and-eql-8de93338c16
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/image_load/image_load_office_dotnet_clr_dll_load.yml
author: Antonlovesdnb, Huntrule Team
date: 2020-02-19
modified: 2023-03-29
tags:
  - attack.execution
  - attack.t1204.002
logsource:
  category: image_load
  product: windows
detection:
  selection:
    Image|endswith:
      - \excel.exe
      - \mspub.exe
      - \outlook.exe
      - \onenote.exe
      - \onenoteim.exe
      - \powerpnt.exe
      - \winword.exe
    ImageLoaded|contains: \clr.dll
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: d13c43f0-f66b-4279-8b2c-5912077c1780
    type: derived

Convert

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

SplunkSPL