Title

No S/Mime interoperability with external clients for message handling. (Cat II impact)

Discussion

In some situations, administrators might wish to use an external program, such as an add-in, to handle S/MIME message decryption. If your organization works with encrypted messages that the decryption functionality in Outlook 2007 cannot handle appropriately, this setting can be used to configure Outlook to hand S/MIME messages off to an external program for decryption. If no external program has been authorized, however, misconfiguring this setting could allow unauthorized and potentially dangerous programs to handle encrypted messages, which could compromise security.

Check Content

The policy value for User Configuration -> Administrative Templates -> Microsoft Office Outlook 2007 -> Security -> Cryptography “S/MIME interoperability with external clients” will be set to “Enabled (Handle internally)”. Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\12.0\Outlook\Security Criteria: If the value ExternalSMime is REG_DWORD = 0, this is not a finding.

Fix Text

The policy value for User Configuration -> Administrative Templates -> Microsoft Office Outlook 2007 -> Security -> Cryptography “S/MIME interoperability with external clients” will be set to “Enabled (Handle internally)”.

Additional Identifiers

Rule ID: SV-19010r1_rule

Vulnerability ID: V-17790

Group Title:

Expert Comments

CCIs tied to check.

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