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T1137.004 Outlook Home Page

Adversaries may abuse Microsoft Outlook’s Home Page feature to obtain persistence on a compromised system. Outlook Home Page is a legacy feature used to customize the presentation of Outlook folders. This feature allows for an internal or external URL to be loaded and presented whenever a folder is opened. A malicious HTML page can be crafted that will execute code when loaded by Outlook Home Page.1

Once malicious home pages have been added to the user’s mailbox, they will be loaded when Outlook is started. Malicious Home Pages will execute when the right Outlook folder is loaded/reloaded.1

Item Value
ID T1137.004
Sub-techniques T1137.001, T1137.002, T1137.003, T1137.004, T1137.005, T1137.006
Tactics TA0003
Platforms Office 365, Windows
Permissions required Administrator, User
Version 1.1
Created 07 November 2019
Last Modified 16 August 2021

Procedure Examples

ID Name Description
G0049 OilRig OilRig has abused the Outlook Home Page feature for persistence. OilRig has also used CVE-2017-11774 to roll back the initial patch designed to protect against Home Page abuse.7
S0358 Ruler Ruler can be used to automate the abuse of Outlook Home Pages to establish persistence.6

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
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.4 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.1

Detection

ID Data Source Data Component
DS0015 Application Log Application Log Content
DS0017 Command Command Execution
DS0009 Process Process Creation

References

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