The ability to display level 1 attachments must be disallowed.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-17671	DTOO240	SV-53941r1_rule		Medium

Description
To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict access to files attached to email messages or other items. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. By default, Outlook completely blocks access to Level 1 files, and requires users to save Level 2 files to disk before opening them. If this configuration is changed, users will be able to open and execute potentially dangerous attachments, which can affect their computers or compromise the confidentiality, integrity, or availability of data.

Description

To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict access to files attached to email messages or other items. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe. By default, Outlook completely blocks access to Level 1 files, and requires users to save Level 2 files to disk before opening them. If this configuration is changed, users will be able to open and execute potentially dangerous attachments, which can affect their computers or compromise the confidentiality, integrity, or availability of data.

STIG	Date
Microsoft Outlook 2013 STIG	2017-03-17

Details

Check Text ( C-47948r1_chk )
Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Security Form Settings -> Attachment Security "Display Level 1 attachments" is set to "Disabled". 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 ShowLevel1Attach is REG_DWORD = 0, this is not a finding.

Check Text ( C-47948r1_chk )

Verify the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Security Form Settings -> Attachment Security "Display Level 1 attachments" is set to "Disabled".

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 ShowLevel1Attach is REG_DWORD = 0, this is not a finding.

Fix Text (F-46841r1_fix)
Set the policy value for User Configuration -> Administrative Templates -> Microsoft Outlook 2013 -> Security -> Security Form Settings -> Attachment Security "Display Level 1 attachments" to "Disabled".