Office Application Startup: Outlook Rules
- ID
- T1137.005
- Tactics
- TA0003 Persistence
- Sub-technique of
- T1137 Office Application Startup
- Platforms
- Windows, Office Suite
- Data sources
- Process Creation, Module Load, Application Log Content, Command Execution
- Source
- attack.mitre.org
- MITRE last modified
- 25 Oct 2025
Adversaries may abuse Microsoft Outlook rules to obtain persistence on a compromised system. Outlook rules allow a user to define automated behavior to manage email messages. A benign rule might, for example, automatically move an email to a particular folder in Outlook if it contains specific words from a specific sender. Malicious Outlook rules can be created that can trigger code execution when an adversary sends a specifically crafted email to that user.[4]
Once malicious rules have been added to the user’s mailbox, they will be loaded when Outlook is started. Malicious rules will execute when an adversary sends a specifically crafted email to the user.[4]
Detection
- DET0095 Detect Persistence via Malicious Outlook Rules
Data components: Process Creation, Module Load, Application Log Content, Command Execution
Mitigations (2)
- 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. [1]
- M1051 Update Software
For the Outlook methods, blocking macros may be ineffective as the Visual Basic engine used for these features is separate from the macro scripting engine.[2] Microsoft has released patches to try to address each issue. Ensure KB3191938 which blocks Outlook Visual Basic and displays a malicious code warning, KB4011091 which disables custom forms by default, and KB4011162 which removes the legacy Home Page feature, are applied to systems.[3]
Software (1)
References
- win10_asr
- SensePost Outlook Forms
- SensePost Outlook Home Page
- SilentBreak Outlook Rules