External content and pictures in HTML email must be displayed.

From Microsoft Outlook 2013 STIG

Part of DTOO270 - External Pictures & content

Associated with: CCI-000366

SV-54042r3_rule External content and pictures in HTML email must be displayed.

Vulnerability discussion

Malicious email senders 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. By default, Outlook does not download external content in HTML email and RSS items unless the content is considered safe. Content that Outlook can be configured to consider safe includes: * Content in email messages from senders and to recipients defined in the Safe Senders and Safe Recipients lists. * Content from websites in Internet Explorer's Trusted Sites security zone. * Content in RSS items.* Content from SharePoint Discussion Boards. Users can control what content is considered safe by changing the options in the Automatic Download section of the Trust Center. If Outlook's default blocking configuration is overridden, in the Trust Center or by some other method, Outlook will display external content in all HTML email messages, including any that include Web beacons.

Check content

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2013 >> Security >> Automatic Picture Download Settings "Display pictures and external content in HTML e-mail" is set to "Enabled". NOTE: When this setting is Enabled, Outlook 2007 does block automatic download of content from external servers unless the sender is included in the Safe Senders list. Recipients can choose to download external content from untrusted senders on a message-by-message basis. 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 BlockExtContent is REG_DWORD = 1, this is not a finding.

Fix text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Automatic Picture Download Settings "Display pictures and external content in HTML e-mail" to "Enabled".

Pro Tips

Lavender hyperlinks in small type off to the right (of CSS class id, if you view the page source) point to globally unique URIs for each document and item. Copy the link location and paste anywhere you need to talk unambiguously about these things.

You can obtain data about documents and items in other formats. Simply provide an HTTP header Accept: text/turtle or Accept: application/rdf+xml.

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