Send all signed messages as clear signed messages must be configured.
An XCCDF Rule
Description
<VulnDiscussion>When users sign email messages with their signing certificate and send them, Outlook uses the sender'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 email 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 email messages.</VulnDiscussion><FalsePositives></FalsePositives><FalseNegatives></FalseNegatives><Documentable>false</Documentable><Mitigations></Mitigations><SeverityOverrideGuidance></SeverityOverrideGuidance><PotentialImpacts></PotentialImpacts><ThirdPartyTools></ThirdPartyTools><MitigationControl></MitigationControl><Responsibility>System Administrator</Responsibility><Responsibility>Information Assurance Officer</Responsibility><IAControls></IAControls>
- ID
- SV-54023r1_rule
- Severity
- Medium
- References
- Updated
Remediation - Manual Procedure
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Send all signed messages as clear signed messages" to "Enabled".