4.1 Ensure the Common Attachment Types Filter is enabled

Information

The Common Attachment Types Filter lets a user block known and custom malicious file types from being attached to emails.

Rationale:

Blocking known malicious file types can help prevent malware-infested files from infecting a host.

Impact:

Blocking common malicious file types should not cause an impact in modern computing environments.

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

Solution

To enable the Common Attachment Types Filter, use the Microsoft 365 Admin Portal:

Click Security to open the Security portal.

Navigate to Threat management, then Policy, select Anti-malware.

Edit the Default profile, then click Edit protection settings at the bottom of the window.

Select Enable the common attachments filter.

Click Save.

To enable the Common Attachment Types Filter, use the Exchange Online PowerShell Module:

Connect to Exchange Online using Connect-ExchangeOnline.

Run the following Exchange Online PowerShell command:

Set-MalwareFilterPolicy -Identity Default -EnableFileFilter $true

Default Value:

off

See Also

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