Windows: AddInUtil.exe LoLBin Executed from Non-Standard Directory

Alerts when AddInUtil.exe (AddInUtil.exe) runs from an uncommon directory path on Windows.

FreeReviewedSigma · Medium · v2

Product: windows
Category: process_creation
Author: Michael McKinley (@McKinleyMike), Tony Latteri (@TheLatteri) (SigmaHQ), DRL 1.1
Published: 2023-09-18
Updated: 2026-07-31

ATT&CK techniques

Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
Defense Evasion
- T1218System Binary Proxy Execution
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process creation where AddInUtil.exe (Addinutil.exe by name or OriginalFileName) is executed from a directory path that does not match common Microsoft .NET framework/WinSxS locations. Attackers may use AddInUtil.exe to blend in with legitimate signed binaries while running code or performing deployment-related actions from unusual paths. The detection relies on Windows process creation telemetry, specifically the executable image path and the OriginalFileName field.

Reporting behind it

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Windows: AddInUtil.exe LoLBin Executed from Non-Standard Directory

Pivot detection · T1218 · 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-detect-addinutil-exe-execution-from-non-standard-directory-6120ac2a

title: "Windows: AddInUtil.exe LoLBin Executed from Non-Standard Directory"
id: 1499a718-f07b-4fbf-80ba-8a31aeba8b3e
status: test
description: This rule flags process creation where AddInUtil.exe (Addinutil.exe by name or OriginalFileName) is executed from a directory path that does not match common Microsoft .NET framework/WinSxS locations. Attackers may use AddInUtil.exe to blend in with legitimate signed binaries while running code or performing deployment-related actions from unusual paths. The detection relies on Windows process creation telemetry, specifically the executable image path and the OriginalFileName field.
references:
  - https://www.blue-prints.blog/content/blog/posts/lolbin/addinutil-lolbas.html
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_addinutil_uncommon_dir_exec.yml
author: Michael McKinley (@McKinleyMike), Tony Latteri (@TheLatteri), Huntrule Team
date: 2023-09-18
modified: 2025-02-24
tags:
  - attack.stealth
  - attack.t1218
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    - Image|endswith: \addinutil.exe
    - OriginalFileName: AddInUtil.exe
  filter_main_legit_location:
    Image|contains:
      - :\Windows\Microsoft.NET\Framework\
      - :\Windows\Microsoft.NET\Framework64\
      - :\Windows\Microsoft.NET\FrameworkArm\
      - :\Windows\Microsoft.NET\FrameworkArm64\
      - :\Windows\WinSxS\
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 6120ac2a-a34b-42c0-a9bd-1fb9f459f348
    type: derived

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