Title

Default message format must be set to use Plain Text. (Cat II impact)

Discussion

Outlook uses HTML as the default email format. HTML format poses a security risk by embedding information into the email itself, which could allow for release of sensitive information. If a user attempted to insert an HTML link into an email message, the link itself may direct to a malicious website. By sending in that format, the recipient would be subject to becoming infected by the malicious website.

Check Content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Mail Format -> Internet Formatting -> Message Format "Set message format" is "Enabled: Plain Text". 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 EditorPreference is REG_DWORD = 65536 (dec), this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Mail Format -> Internet Formatting -> Message Format "Set message format" to "Enabled: Plain Text".

Additional Identifiers

Rule ID: SV-54062r1_rule

Vulnerability ID: V-26634

Group Title: DTOO314 - Set message format

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.