Sigma rule: GAC DLL Loaded Via Office Applications

Rule

Title

GAC DLL Loaded Via Office Applications

Status

test

Level

high

Author

Antonlovesdnb

Date

2020-02-19

Modified

2023-02-10

File

rules/windows/image_load/image_load_office_dotnet_gac_dll_load.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

Detects any GAC DLL being loaded by an Office Product

Log source

product

windows

category

image_load

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

False positives (as the rule lists them)

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

Tags

• attack.execution
• attack.t1204.002

MITRE ATT&CK ids this rule names

• T1204.002

References

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

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/image_load/image_load_office_dotnet_gac_dll_load.yml