Skip to content

T1137.006 Add-ins

Adversaries may abuse Microsoft Office add-ins to obtain persistence on a compromised system. Office add-ins can be used to add functionality to Office programs. 3 There are different types of add-ins that can be used by the various Office products; including Word/Excel add-in Libraries (WLL/XLL), VBA add-ins, Office Component Object Model (COM) add-ins, automation add-ins, VBA Editor (VBE), Visual Studio Tools for Office (VSTO) add-ins, and Outlook add-ins. 21

Add-ins can be used to obtain persistence because they can be set to execute code when an Office application starts.

Item Value
ID T1137.006
Sub-techniques T1137.001, T1137.002, T1137.003, T1137.004, T1137.005, T1137.006
Tactics TA0003
Platforms Office Suite, Windows
Version 1.2
Created 07 November 2019
Last Modified 24 October 2025

Procedure Examples

ID Name Description
S0268 Bisonal Bisonal has been loaded through a .wll extension added to the %APPDATA%\microsoft\word\startup\ repository.6
S1143 LunarLoader LunarLoader has the ability to use Microsoft Outlook add-ins to establish persistence. 7
S1142 LunarMail LunarMail has the ability to use Outlook add-ins for persistence.7
G0019 Naikon Naikon has used the RoyalRoad exploit builder to drop a second stage loader, intel.wll, into the Word Startup folder on the compromised host.8

Mitigations

ID Mitigation Description
M1040 Behavior Prevention on Endpoint On Windows 10, enable Attack Surface Reduction (ASR) rules to prevent Office applications from creating child processes and from writing potentially malicious executable content to disk. 5

References

  1. Caban, D. and Hirani, M. (2018, October 3). You’ve Got Mail! Enterprise Email Compromise. Retrieved November 17, 2024. ↩

  2. Knowles, W. (2017, April 21). Add-In Opportunities for Office Persistence. Retrieved November 17, 2024. ↩

  3. Microsoft. (n.d.). Add or remove add-ins. Retrieved July 3, 2017. ↩

  4. Shukrun, S. (2019, June 2). Office Templates and GlobalDotName - A Stealthy Office Persistence Technique. Retrieved August 26, 2019. ↩

  5. Microsoft. (2021, July 2). Use attack surface reduction rules to prevent malware infection. Retrieved June 24, 2021. ↩

  6. Mercer, W., et al. (2020, March 5). Bisonal: 10 years of play. Retrieved January 26, 2022. ↩

  7. Jurčacko, F. (2024, May 15). To the Moon and back(doors): Lunar landing in diplomatic missions. Retrieved June 26, 2024. ↩↩

  8. CheckPoint. (2020, May 7). Naikon APT: Cyber Espionage Reloaded. Retrieved May 26, 2020. ↩