DTOO273 - IE Trusted Zones assumed trusted must be blocked.

Information

Malicious users can send HTML email messages with embedded Web beacons, which are pictures and other content from external servers that can be used to track whether specific recipients open the 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 reduce the risk from Web beacons, Outlook disables external content in email messages by default, unless the content is considered 'safe' as determined by the check boxes in the Automatic Download section of the Trust Center. Depending on how these options are configured, safe content can include content in messages from addresses defined in the Safe Senders and Safe Recipients Lists used by the Junk email filter, content from SharePoint discussion boards, and content from websites in the Trusted sites zone in Internet Explorer.
By default, Outlook considers trusted sites from Internet Explorer safe, and automatically downloads content from them, which could potentially include Web beacons.

Solution

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Automatic Picture Download Settings 'Block Trusted Zones' to 'Enabled'.

See Also

https://iasecontent.disa.mil/stigs/zip/U_MS_Outlook_2013_V1R12_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-18, CAT|II, CCI|CCI-000366, Rule-ID|SV-54047r1_rule, STIG-ID|DTOO273, Vuln-ID|V-17564

Plugin: Windows

Control ID: 2ec3bb52068166eddc870d14a315ca60222cc760271620dd3c24f2f08cd8afa5