Title

Automatic download content for email in Safe Senders list must be disallowed. (Cat II impact)

Discussion

Malicious email senders can send HTML email messages with embedded Web beacons, or pictures and other content from external servers that can be used to track whether specific recipients have opened a message. Viewing an email message that contains a Web beacon provides confirmation that the recipient's email address is valid, which leaves the recipient vulnerable to additional spam and harmful email. To help protect users from Web beacons, Outlook can be configured to automatically block the display of external content in email messages. However, because this configuration could block desirable content from display, Outlook can also be configured to automatically display external content in any messages sent by people who are listed in users' Safe Senders Lists or Safe Recipients Lists. By default, Outlook automatically displays external content in email messages from people listed in users' Safe Senders Lists or Safe Recipients Lists, and automatically blocks external content in other messages. If a malicious sender is accidentally added to a user's Safe Senders List or Safe Recipients List, Outlook will display external content in all email messages from the malicious sender, which could include Web beacons.

Check Content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Automatic Picture Download Settings "Automatically download content for e-mail from people in Safe Senders and Safe Recipients Lists" is set to "Disabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\15.0\outlook\options\mail Criteria: If the value UnblockSpecificSenders is REG_DWORD = 0, this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Automatic Picture Download Settings "Automatically download content for e-mail from people in Safe Senders and Safe Recipients Lists" to "Disabled".

Additional Identifiers

Rule ID: SV-54044r1_rule

Vulnerability ID: V-17739

Group Title: DTOO271 - Auto Download from Safe lists

Expert Comments

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