Detecting who is changing Alert Suppression rules in Azure Defender

Published Mar 26 2021 05:09 AM 2,350 Views
Microsoft

One common characteristic of recent attacks is the attempt to evade detection by using different techniques. To evade security software and analyst tools, some malware will enumerate the target system looking for certain running processes, loaded drivers, and registry keys, with the goal of disabling them. When using a Cloud Workload Protection Platform (CWPP) such as Azure Defender, you will have different levels of threat detections according to the plan that you are using. The available plans are:

 

There are some scenarios in which the alert that you are receiving in Azure Defender could be a false positive for your environment. If you want to avoid receiving that specific alert, you can create an alert suppression rule. Although the alert suppression is a feature that can be used to optimize your experience, it can also be used with malicious intent in case a user wants to evade detection. To create or delete alert suppression rules, you need to be Security admin or Subscription Owner. If you just need to view the rules, you need to be Security reader or Reader.

 

Hardening Alert Suppression Creation

If you don’t want to give full Security Admin access to an individual but you still want that individual to create suppression rules, you should create a custom Azure Role with only the necessary privilege to do that. To be able to create alert suppression rules, the user must have the following privilege:

 

Role.JPG

In addition, you should also give Reader role privilege to allow the user to see the alert suppression rules that exist.

 

Tracking changes to suppression rules

After hardening the privilege to create suppression rules, you can start tracking changes. To do that, you will use Azure Activity Log. The operation that has the alert suppression creation is shown below:

 

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You can open this operation and look at the JSON tab to obtain more details. You will see the name of the rule that was created or modified, as shown in the example below:

 

Fig4.JPG

 

At this point you can also create a new Alert rule in Azure Activity Log using the New alert rule option in the summary tab, as shown below:

 

Fig5.JPG

 

To learn more about how to create alerts using Azure Activity Log, read this article.  If you are ingesting Azure Activity Log in Azure Sentinel, you can also create an incident based on this operation.

 

Reviewer

Tal Rosler, Program Manager

 

Co-Authors
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