Potential Persistence Via Microsoft Office Add-In

Detects potential persistence activity via startup add-ins that load when Microsoft Office starts (.wll/.xll are simply .dll fit for Word or Excel).

title: Potential Persistence Via Microsoft Office Add-In
id: 8e1cb247-6cf6-42fa-b440-3f27d57e9936
status: test
description: Detects potential persistence activity via startup add-ins that load when Microsoft Office starts (.wll/.xll are simply .dll fit for Word or Excel).
references:
    - Internal Research
    - https://labs.withsecure.com/publications/add-in-opportunities-for-office-persistence
    - https://github.com/redcanaryco/atomic-red-team/blob/4ae9580a1a8772db87a1b6cdb0d03e5af231e966/atomics/T1137.006/T1137.006.md
author: NVISO
date: 2020-05-11
modified: 2023-02-08
tags:
    - attack.persistence
    - attack.t1137.006
logsource:
    category: file_event
    product: windows
detection:
    selection_wlldropped:
        TargetFilename|contains: '\Microsoft\Word\Startup\'
        TargetFilename|endswith: '.wll'
    selection_xlldropped:
        TargetFilename|contains: '\Microsoft\Excel\Startup\'
        TargetFilename|endswith: '.xll'
    selection_xladropped:
        TargetFilename|contains: 'Microsoft\Excel\XLSTART\'
        TargetFilename|endswith: '.xlam'
    selection_generic:
        TargetFilename|contains: '\Microsoft\Addins\'
        TargetFilename|endswith:
            - '.xlam'
            - '.xla'
            - '.ppam'
    condition: 1 of selection_*
falsepositives:
    - Legitimate add-ins
level: high

• T1137.006Add-ins

• Internal Research
• https://labs.withsecure.com/publications/add-in-opportunities-for-office-persistence↗
• https://github.com/redcanaryco/atomic-red-team/blob/4ae9580a1a8772db87a1b6cdb0d03e5af231e966/atomics/T1137.006/T1137.006.md↗