Detections
Analytics
1.13.3.1.4 Ensure 'Do not prompt about Level 1 attachments when sending an item' is set to Disabled
Information
This policy setting controls whether Outlook displays a warning before sending an item that contains an unsafe attachment that will be blocked when the item is opened by a recipient. 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. 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 a user sends an item with a Level 1 attachment, which can cause users' data to be at risk.
If you disable or do not configure this policy setting, when users attempt to send an item to which a level 1 file has been attached, Outlook warns them that the message contains a potentially unsafe attachment and that the recipient might not be able to access it.
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. 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 users attempt to send an item to which a level 1 file has been attached, Outlook warns them that the message contains a potentially unsafe attachment and that the recipient might not be able to access it. If this configuration is changed, Outlook will not display the warning when users send such items, which 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 sending 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: e35382b661213ad1e572e30bfb242b1b4b269e8cfbf045ff1592c00d087e38fb