Title

All signed messages as clear signed messages must be configured. (Cat II impact)

Discussion

When users sign e-mail messages with their digital signature and send them, Outlook uses the signature's private key to encrypt the digital signature but sends the messages as clear text, unless they are encrypted separately. If users change this functionality by clearing the Send clear text signed message when sending signed messages option in the E-mail Security section of the Trust Center, any recipients who are unable to access or use the sender's digital certificate will not be able to read the e-mail messages.

Check Content

The policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2010 -> Security -> Cryptography “Send all signed messages as clear signed messages” must be set to “Enabled”. Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\14.0\outlook\security Criteria: If the value ClearSign is REG_DWORD = 1, this is not a finding.

Fix Text

Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2010 -> Security -> Cryptography “Send all signed messages as clear signed messages” to “Enabled”.

Additional Identifiers

Rule ID: SV-33570r1_rule

Vulnerability ID: V-17800

Group Title: DTOO264 - Clear signed messages

Expert Comments

CCIs tied to check.

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