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New alert policies in Microsoft Defender for Office 365

Microsoft Defender for Office 365 is introducing new and improved alert policies related to post-delivery detections. This includes enhancements to the Automated Investigation & Response (AIR) playbooks associated with them. In addition, we're modifying the severity classification for six default alert policies to better align the alerts generated by these policies with their impact on your organization.

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Post-delivery detections

We'll be introducing four new default alert policies related to post-delivery detections after the Microsoft Defender for Office 365 Zero-hour auto purge (ZAP) removes messages from an inbox. These four new alert policies will replace two existing default alert policies that cover ZAP scenarios and will provide organizations enhanced details about the underlying detection and related indicators. These alerts (and the AIR playbooks that will be triggered from these alerts) will accurately capture the threats of the emails and entities, including if the URL points to a malicious file or if the file contains a malicious URL.

The following table lists the new alert policies and the existing alert policies that will be removed. See the How this will affect your organization section for details about the rollout.

New or existing alert policy Alert policy name Alert policy ID
New Email messages containing malicious URL removed after delivery 8e6ba277-ef39-404e-aaf1-294f6d9a2b88
New Email messages containing malicious file removed after delivery 4b1820ec-39dc-45f3-abf6-5ee80df51fd2
New Email messages from a campaign were delivered and later removed c8522cbb-9368-4e25-4ee9-08d8d899dfab
New Email messages removed after delivery b8f6b088-5487-4c70-037c-08d8d71a43fe
Existing (will be removed) Email messages containing phish URLs removed after delivery EA8169FA-0678-4751-8854-AEBEA7ADECEB
Existing (will be removed) Email messages containing malware removed after delivery 0179B3F7-3FDA-40C3-8F24-278563978DBB

Alert severity enhancements

For the following table identifies the default alert policies whose severity classifications are being modified. We're changing the severity classification for these alert policies to better align with the potential risk and impact on your organization and to help your security teams prioritize the alerts generated by these policies.

Alert Alert policy ID Old severity New severity
Suspicious email forwarding activity BFD48F06-0865-41A6-85FF-ADB746423EBF Medium High
Email reported by user as malware or phish B26A5770-0C38-434A-9380-3A3C2C27BBB3 Informational Low
Unusual increase in email reported as phish A00D8C62-9320-4EEA-A7E5-966B9AC09558 High Medium
Admin Submission result completed AE9B83DD-6039-4EA9-B675-6B0AC3BF4A41 Low Informational
Creation of forwarding/redirect rule D59A8FD4-1272-41EE-9408-86F7BCF72479 Low Informational
eDiscovery search started or exported 6FDC5710-3998-47F0-AFBB-57CEFD7378A Medium Informational

When will these changes happen

The following table identifies when the new alert policies will begin triggering post-delivery alerts. The table also identifies when the two existing alert policies will be removed.

Alert policy Date
Email messages containing malicious URL removed after delivery (new) Alerts will start triggering on April 11, 2021
Email messages containing malicious file removed after delivery (new) Alerts will start triggering on April 11, 2021
Emails messages from a campaign were delivered and later removed (new) Alerts will start triggering on May 28, 2021
Malicious emails were delivered and later removed (new) Alerts will start triggering on May 28, 2021
Email messages containing phish URLs removed after delivery (existing, will be removed) The alert policy was removed in June 2021. See the What you need to do to prepare for these changes section.
Email messages containing malware removed after delivery (existing, will be removed) The alert policy was removed in June 2021. See the What you need to do to prepare for these changes section.

The alert severity changes will be rolled out to all organizations by May 14, 2021.

How this will affect your organization

The new alerts will begin firing, and triggering the AIR investigations in your organization on the dates listed above. To reduce the impact on security organizations that have operationalized the two alerts that are to be removed, you'll see alerts triggered by the existing alert policies and the alerts triggered by the new alert policies between April 5, 2021 and May 28, 2021. This is to provide security teams with time to handle the required changes. To help security teams with the increased alert volume during this short duration, both the existing alerts and the new alerts will be correlated into the same AIR investigation and correlated into a same Incident. More specifically, this includes the following behavior for alerts, AIR investigations, and Incidents:

  • Alerts: By design, you'll see the following alert pairs across the existing and new alerts:

    • Email messages containing phish URLs removed after delivery AND Email messages containing malicious URL removed after delivery

    • Email messages containing malware removed after delivery AND Email messages containing malicious file removed after delivery

    Alert pairs for new and existing alerts.

    For more information about managing these alert pairs, see the What you need to do to prepare for these changes section.

  • AIR Investigations: Alerts will be correlated into a single AIR Investigation, with one of the alerts classified as "triggering" and the other as "repeated".

    Alert pairs in AIR Investigations.

  • Incidents: Both alerts will correlate into the same Incident

    Alert pairs in Incidents.

What you need to do to prepare for these changes

How your organization utilizes these alerts will determine what you need to do to prepare. If you've operationalized the alerts and are using or consuming them either through an API, an alert email notification, or in the Microsoft Purview compliance portal or the Microsoft Defender portal, you'll need to modify your workflows.

If you haven't operationalized these alerts, you can do one of the following:

  • Disable the following alert policies (that are being removed) to reduce alert volume in your organization:

    • Email messages containing phish URLs removed after delivery

    • Email messages containing malware removed after delivery

  • Do nothing. We'll disable the existing alert policies on May 28, 2021.

If you have operationalized these alerts:

  • Start consuming the new alerts as a part of your workflows, in anticipation of the existing alert policy removal on May 28, 2021. If you have custom logic in your ticketing system, a security mailbox where you receive alert email notifications, or a SIEM solution that depends on the alert name or alert policy ID (CorrelationId), you'll need to modify the logic to accommodate the change.

    Note

    The information in the alerts, investigations, and incidents has not changed. In fact, this information has been enhanced with additional detail about the threats associated with them.

  • After you've made the modifications, you can disable the existing alert policies to reduce alert volume in your organization:

    • Email messages containing phish URLs removed after delivery

    • Email messages containing malware removed after delivery

    Alternatively, you can leave these alert policies enabled until we delete them on May 28, 2021.