Title

Dragging Unicode email messages to file system must be disallowed. (Cat II impact)

Discussion

When users drag email messages from Outlook to a Windows Explorer window or to their Desktop, Outlook creates an .msg file using the native character encoding format for the configured locale (the so-called "ANSI" format). If this setting is Enabled, Outlook uses the Unicode character encoding standard to create the message file, which preserves special characters in the message. However, Unicode text is vulnerable to homograph attacks, in which characters are replaced by different but similar-looking characters. For example, the Cyrillic letter "?" (U+0430) appears identical to the Latin letter "a" (U+0061) in many typefaces, but is actually a different character. Homographs can be used in "phishing" attacks to convince victims to visit fraudulent websites and enter sensitive information.

Check Content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Other -> Advanced "Use Unicode format when dragging e-mail message to file system" 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\general Criteria: If the value MSGFormat is REG_DWORD = 0, this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Outlook Options -> Other -> Advanced "Use Unicode format when dragging e-mail message to file system" to "Disabled".

Additional Identifiers

Rule ID: SV-242688r960963_rule

Vulnerability ID: V-242688

Group Title: SRG-APP-000141

Expert Comments

CCIs tied to check.

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