2.1.6 (L1) Ensure Exchange Online Spam Policies are set to notify administrators

Information

In Microsoft 365 organizations with mailboxes in Exchange Online or standalone Exchange Online Protection (EOP) organizations without Exchange Online mailboxes, email messages are automatically protected against spam (junk email) by EOP.

Configure Exchange Online Spam Policies to copy emails and notify someone when a sender in the organization has been blocked for sending spam emails.

A blocked account is a good indication that the account in question has been breached and an attacker is using it to send spam emails to other people.

Solution

To remediate using the UI:

- Navigate to Microsoft 365 Defender

https://security.microsoft.com

.
- Click to expand Email & collaboration select Policies & rules > Threat policies
- Under Policies select Anti-spam
- Click on the Anti-spam outbound policy (default)
- Select Edit protection settings then under Notifications
- Check Send a copy of suspicious outbound messages or message that exceed these limits to these users and groups then enter the desired email addresses.
- Check Notify these users and groups if a sender is blocked due to sending outbound spam then enter the desired email addresses.
- Click Save

To remediate using PowerShell:

- Connect to Exchange Online using Connect-ExchangeOnline
- Run the following PowerShell command:

$BccEmailAddress = @("<INSERT-EMAIL>")

$NotifyEmailAddress = @("<INSERT-EMAIL>")

Set-HostedOutboundSpamFilterPolicy -Identity Default -BccSuspiciousOutboundAdditionalRecipients $BccEmailAddress -BccSuspiciousOutboundMail $true -NotifyOutboundSpam $true -NotifyOutboundSpamRecipients $NotifyEmailAddress

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 users that have been blocked should not cause an impact to the user.

See Also

https://workbench.cisecurity.org/benchmarks/17682

Item Details

Category: INCIDENT RESPONSE

References: 800-53|IR-1, 800-53|IR-8, CSCv7|7.9, CSCv7|7.10

Plugin: microsoft_azure

Control ID: 0475e92a92843080c7020e8576dbe3cd272c2e1b6edd18c9085e37045409ccd0