Windows Office Apps Loading .NET Assembly DLLs from C:\Windows\assembly

Alerts when Office applications load DLLs from C:\Windows\assembly\ via image load events.

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 image load events where Microsoft Office executables (Excel, PowerPoint, Word, Outlook, OneNote, Publisher) load a DLL from the Windows .NET assembly cache path (C:\Windows\assembly\). Adversaries may leverage Office to trigger execution via .NET assemblies loaded by the Office process. Detection relies on Windows image load telemetry that provides the loading process image path and the loaded DLL path.

Reporting behind it

Related detections9 linkedT1204.002 — drag to rearrange

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Windows Office Apps Loading .NET Assembly DLLs from C:\Windows\assembly

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-office-apps-load-net-dlls-from-c-windows-assembly-ff0f2b05

title: Windows Office Apps Loading .NET Assembly DLLs from C:\Windows\assembly
id: 5cf5b92f-68ce-4b3d-8b1c-7af2dece080d
status: test
description: This rule flags image load events where Microsoft Office executables (Excel, PowerPoint, Word, Outlook, OneNote, Publisher) load a DLL from the Windows .NET assembly cache path (C:\Windows\assembly\). Adversaries may leverage Office to trigger execution via .NET assemblies loaded by the Office process. Detection relies on Windows image load telemetry that provides the loading process image path and the loaded DLL path.
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_assembly_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
      - \onenote.exe
      - \onenoteim.exe
      - \outlook.exe
      - \powerpnt.exe
      - \winword.exe
    ImageLoaded|startswith: C:\Windows\assembly\
  condition: selection
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: ff0f2b05-09db-4095-b96d-1b75ca24894a
    type: derived

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