4.4 Ensure automatic forwarding options are disabled

Information

You should disable automatic forwarding to prevent users from auto-forwarding mail through Outlook and Outlook on the Web.

Rationale:

In the event that an attacker gains control of an end-user account they could create rules to ex-filtrate data from your environment.

Impact:

Care should be taken before implementation to ensure there is no business need for case-by-case auto-forwarding. Disabling auto-forwarding to remote domains will affect all users and in an organization.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

To perform remediation you may use the Exchange Online PowerShell Module:

Connect to Exchange online using Connect-ExchangeOnline.

Run the following Powershell to disable auto-forwarding to remote domains:

Set-RemoteDomain Default -AutoForwardEnabled $false

Run the following Powershell to verify AutoForwardEnabled is now set to False.

Get-RemoteDomain Default | fl AllowedOOFType, AutoForwardEnabled

Default Value:

True

See Also

https://workbench.cisecurity.org/files/3433