New Override Alerts for Office 365 Create an Additional Safety Net

When getting started with your new Office 365 tenant, Microsoft has done a respectable job of making the first run experience not too overwhelming. But as your tenant grows, more people are added to roles that can impact policy, it’s possible that a rule could be created that will allow a malicious email or file to be delivered to a mailbox.

As an example, you may set a policy to enable a specific IP to deliver email but if an attacker is able to exploit this policy to deliver a phishing email, you may not be aware of the intrusion. This is the gap that Microsoft is trying to address with its new override alerts.

Announced today and the feature will start rolling out in early February, for those using Microsoft Defender for Office 365 Plan 1 and Plan 2, you will now be alerted when a message is delivered, only when it is determined with a high degree of confidence that it is phishing or malware, to a mailbox because of a policy that was enabled/disabled.

Specifically, Microsoft says that the “new system alert policies will enable security admins to receive alerts if a message with a high confidence phish or malware verdict is delivered to a mailbox due to one of the following” scenarios:

  • Phish delivered due to an IP allow policy
  • Phish delivered due to an ETR override.
  • Phish delivered because a user’s Junk Mail Folder is disabled.
  • Phish not zapped because ZAP is disabled.
  • Malware not zapped because ZAP is disabled.

When this feature rolls out, the alert policies will be enabled by default but you can turn them on/off as needed. You will also have the ability to define who gets the alerts and also manage how many alerts are sent to help control false positives.

This looks to be a smart move by Microsoft to help contain malware/phishing in an environment where controls may not be correctly applied. Further, this is a safety net and even though it will not be perfect, this is a good step to help to prevent accidental exposure inside your tenant.