5.1.7 Set 'Do not prompt about Level 1 attachments when closing an item' 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.)
Important- This policy setting only applies if the 'Outlook Security Mode' policy setting
under 'Microsoft Outlook 2010\Security\Security Form Settings' is configured to 'Use
Outlook Security Group Policy.' The recommended state for this setting is- Disabled.

*Rationale*

To protect users from viruses and other harmful files, Outlook 2010 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 2010\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 2010, 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 2010\Security\Security Form Settings\Microsoft Office
Outlook 2010 Security and select Use Outlook Security Group Policy from the drop-down
list.

See Also

https://workbench.cisecurity.org/files/530

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6b.

Plugin: Windows

Control ID: 2c60d909099411b18aad66a263c5fbadbc5ce9e4d5b3e271d76572368d7c3def