GAC DLL Loaded Via Office Applications — Sigma Rule

Rule metadata and linked tags

Author: Antonlovesdnb. Source status: test; severity: high. Source dates: 2020-02-19 / 2023-02-10.

{
  "category": "image_load",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 7b12046e2943726716f5d4fa2b69914215dd4a77d730d13c81a1d387b0fb963e

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: GAC DLL Loaded Via Office Applications
id: 90217a70-13fc-48e4-b3db-0d836c5824ac
status: test
description: Detects any GAC DLL being loaded by an Office Product
references:
    - https://medium.com/threatpunter/detecting-adversary-tradecraft-with-image-load-event-logging-and-eql-8de93338c16
author: Antonlovesdnb
date: 2020-02-19
modified: 2023-02-10
tags:
    - attack.execution
    - attack.t1204.002
logsource:
    category: image_load
    product: windows
detection:
    selection:
        Image|endswith:
            - '\excel.exe'
            - '\mspub.exe'
            - '\onenote.exe'
            - '\onenoteim.exe' # Just in case
            - '\outlook.exe'
            - '\powerpnt.exe'
            - '\winword.exe'
        ImageLoaded|startswith: 'C:\Windows\Microsoft.NET\assembly\GAC_MSIL'
    condition: selection
falsepositives:
    - Legitimate macro usage. Add the appropriate filter according to your environment
level: high

Original YAML and metadata in JSON

False positives

• Legitimate macro usage. Add the appropriate filter according to your environment

Source references

• https://medium.com/threatpunter/detecting-adversary-tradecraft-with-image-load-event-logging-and-eql-8de93338c16