Title

Message formats must be set to use SMime. (Cat II impact)

Discussion

Email typically travels over open networks and is passed from server to server. Messages are therefore vulnerable to interception, and attackers might read or alter their contents. It is therefore important to have a mechanism for signing messages and providing end-to-end encryption. Outlook supports three formats for encrypting and signing messages: S/MIME, Exchange, and Fortezza. By default, Outlook only uses S/MIME to encrypt and sign messages. When an organization has policies that mandate the use of specific encryption formats, allowing users to choose freely between these formats could cause them to violate such policies.

Check Content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Message Formats" is set to "Enabled (S\MIME)". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\15.0\outlook\security Criteria: If the value MsgFormats is REG_DWORD = 1, this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Message Formats" to "Enabled (S\MIME)".

Additional Identifiers

Rule ID: SV-54004r1_rule

Vulnerability ID: V-17755

Group Title: DTOO260 - SMime message formats

Expert Comments

CCIs tied to check.

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