Warning about invalid signatures must be enforced.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-17803	DTOO265	SV-54024r1_rule		Medium

Description
If users open email messages that include invalid digital signatures, Outlook displays a warning dialog box. Users can decide whether they want to be warned about invalid signatures in the future. If users are not notified about invalid signatures, they might be prevented from detecting a fraudulent signature sent by a malicious person.

STIG	Date
Microsoft Outlook 2013 STIG	2017-03-17

Details

Check Text ( C-47977r1_chk )
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Signature Warning" is "Enabled (Always warn about invalid signatures)". 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 WarnAboutInvalid is REG_DWORD = 1, this is not a finding.

Check Text ( C-47977r1_chk )

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Signature Warning" is "Enabled (Always warn about invalid signatures)".

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 WarnAboutInvalid is REG_DWORD = 1, this is not a finding.

Fix Text (F-46910r1_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Cryptography "Signature Warning" to "Enabled (Always warn about invalid signatures)".