O365-OU-000015 - The ability to demote attachments from Level 2 to Level 1 must be 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\14.0\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\14.0\Outlook\Security\Level1Remove registry key has no effect.

Solution

Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Security >> Security Form Settings >> Attachment Security >> Allow users to demote attachments to Level 2 to 'Disabled'.

See Also

https://dl.dod.cyber.mil/wp-content/uploads/stigs/zip/U_MS_Office_365_ProPlus_V3R1_STIG.zip

Item Details

Category: SYSTEM AND COMMUNICATIONS PROTECTION

References: 800-53|SC-18(1), CAT|II, CCI|CCI-001662, Rule-ID|SV-223360r961086_rule, STIG-ID|O365-OU-000015, STIG-Legacy|SV-108899, STIG-Legacy|V-99795, Vuln-ID|V-223360

Plugin: Windows

Control ID: 73942a79885fbc57d749dd31957e18ad5322d5e2ba9f5bd79ce888f9d1467f37