Detections
Analytics
1.13.3.1.1 Ensure 'Allow users to demote attachments to Level 2' is set to Disabled
Information
This policy setting controls whether Outlook users can demote attachments to Level 2 by using a registry key, which will allow them to save files to disk and open them from that location. Outlook uses two levels of security to restrict access to files attached to e-mail messages or other items. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2.If you enable this policy setting, users can create a list of Level 1 file types to demote to Level 2 by adding the file types to the following registry key: HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security\Level1Remove.
If you disable or do not configure this policy setting, users cannot demote level 1 attachments to level 2, and the HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Security\Level1Remove registry key has no effect. The recommended state for this setting is: Disabled.
Rationale:
Outlook uses two levels of security to restrict access to files attached to e-mail messages or other items. Files with specific extensions can be categorized as Level 1 (users cannot view the file) or Level 2 (users can open the file after saving it to disk). Users can freely open files of types that are not categorized as Level 1 or Level 2.
By default, Outlook does not allow users to demote file types from Level 1 to Level 2. If this setting is Enabled, users can create a list of Level 1 file types to demote to Level 2 by adding the file types to the following registry key:
HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\15.0\Security\Level1Remove
If users can demote Level 1 files to Level 2, they will be able to access potentially dangerous files after saving them to disk, which could allow malicious code to affect their computers or compromise the security of sensitive information.
Solution
To implement the recommended configuration state, set the following Group Policy setting to Disabled.User Configuration\Administrative Templates\Microsoft Outlook 2016\Security\Security Form Settings\Attachment Security\Allow users to demote attachments to Level 2
Impact:
Allowing users to demote attachments to Level 2 can pose a significant risk. Unless your users have a legitimate business need for such functionality, this setting should be disabled.
See Also
Item Details
Audit Name: CIS Microsoft Office Outlook 2016 v1.1.0 Level 1
Category: CONFIGURATION MANAGEMENT
References: 800-53|CM-6b.
Plugin: Windows
Control ID: 4ef25a3d993fcc7b47bd034a81efb69f858a474ef137fc468d478ffbe7ce0e4e