1.13.3.1.2 Ensure 'Display Level 1 attachments' is set to Disabled

Information

This policy setting controls whether Outlook blocks potentially dangerous attachments designated Level 1. 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 e-mail 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.

The recommended state for this setting is: Disabled.

Rationale:

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 e-mail 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.

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\Display Level 1 attachments

Impact:

See Attachment file types restricted by Office for the full list of file types classified Level 1 by default.

Important For this setting to apply, you must also enable the 'Outlook Security Mode' setting in User Configuration\Administrative Templates\Classic Administrative Templates (ADM)\Microsoft Office Outlook <version>\Security\Security Form Settings\Microsoft Office Outlook Security and select Use Outlook Security Group Policy from the drop-down list.

See Also

https://workbench.cisecurity.org/files/553

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-18(4)

Plugin: Windows

Control ID: b34e895dee93e4c78a4331db92e6158498f5aaec9d789c2115da7c225a388275