Information
Exchange Online Protection (EOP) is the cloud-based filtering service that protects your organization against spam, malware, and other email threats. EOP is included in all Microsoft 365 organizations with Exchange Online mailboxes.
EOP uses flexible anti-malware policies for malware protection settings. These policies can be set to notify Admins of malicious activity.
Rationale:
This setting alerts administrators that an internal user sent a message that contained malware. This may indicate an account or machine compromise, that would need to be investigated.
Note: Audit and Remediation guidance may focus on the Default policy however, if a Custom Policy exists in the organization's tenant then ensure the setting is set as outlined in the highest priority policy listed.
Impact:
Notification of account with potential issues should not cause an impact to the user.
NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.
Solution
To enable notifications for internal users sending malware, use the Microsoft 365 Admin Center:
Click Security to open the Security portal.
Under Email & collaboration navigate to Policies & rules > Threat policies.
Select Anti-malware.
Click on the Default policy.
Click on Edit protection settings and change the settings for Notify an admin about undelivered messages from internal senders to On and enter the email address of the administrator who should be notified under Administrator email address.
To check the setting from PowerShell, use the Exchange Online Module for PowerShell
Connect to Exchange Online by using the Connect-ExchangeOnline.
Run the following command:
set-MalwareFilterPolicy -Identity '{Identity Name}' -EnableInternalSenderAdminNotifications $True -InternalSenderAdminAddress {[email protected]}