Detections
Analytics
1.13.3.1.3 Ensure 'Do not prompt about Level 1 attachments when closing an item' is set to Disabled
Information
This policy setting controls whether Outlook displays a warning before closing an item that contains an unsafe attachment that will be blocked when the item is re-opened. To protect users from viruses and other harmful files, Outlook uses two levels of security, designated Level 1 and Level 2, to restrict users' access to files attached to e-mail messages or other items. Outlook completely blocks access to Level 1 files by default, and requires users to save Level 2 files to disk before opening them. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe.If you enable this policy setting, Outlook will not display a warning when users close items with Level 1 attachments, which could cause data loss.
If you disable or do not configure this policy setting, when a user closes an item to which a level 1 file has been attached, Outlook warns the user that the message contains a potentially unsafe attachment and that the user might not be able to access the attachment when opening the item later. (Such a sequence of events might occur when a user closes a draft message that they intend to resume editing at some future time.)
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 users' access to files attached to e-mail messages or other items. Outlook completely blocks access to Level 1 files by default, and requires users to save Level 2 files to disk before opening them. Potentially harmful files can be classified into these two levels by file type extension, with all other file types considered safe.
By default, when a user closes an item to which a level 1 file has been attached, Outlook warns the user that the message contains a potentially unsafe attachment and that the user might not be able to access the attachment when opening the item later. (Such a sequence of events might occur when a user closes a draft message that they intend to resume editing at some future time.) If this configuration is changed, Outlook will not display the warning when the user closes the item but will still block the unsafe attachment if the user opens the message later. This functionality can cause users to lose access to important 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\Do not prompt about Level 1 attachments when closing an item
Impact:
Disabling this setting enforces the default configuration in Outlook, and therefore is unlikely to cause usability issues for most users.
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
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: efacb172e635553da8178d2fc7ca24a9d344259c7d150102d6850578db8c471e