Title

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

Discussion

This policy setting controls whether Outlook sends signed messages as clear text signed messages. If you enable this policy setting, the "Send clear text signed message when sending signed messages" option is selected in the E-mail Security section of the Trust Center. If you disable or do not configure this policy setting, 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.

Check Content

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2016 -> Security -> Cryptography "Send all signed messages as clear signed messages" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\16.0\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 2016 -> Security -> Cryptography "Send all signed messages as clear signed messages" to "Enabled".

Additional Identifiers

Rule ID: SV-228455r508021_rule

Vulnerability ID: V-228455

Group Title: SRG-APP-000516

Expert Comments

CCIs tied to check.

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