Information
Microsoft Defender for DNS scans all network traffic exiting from within a subscription.
Rationale:
DNS lookups within a subscription are scanned and compared to a dynamic list of websites that might be potential security threats. These threats could be a result of a security breach within your services, thus scanning for them could prevent a potential security threat from being introduced.
Impact:
Enabling Microsoft Defender for DNS requires enabling Microsoft Defender for your subscription. Both will incur additional charges, with Defender for DNS being a small amount per million queries.
Solution
From Azure Portal
Go to Microsoft Defender for Cloud
Select Environment Settings blade
Click on the subscription name
Select the Defender plans blade
On the line in the table for DNS Select On under Plan.
Select 'Save
From Powershell
Use the below command to enable Standard pricing tier for App Service
az security pricing create -n 'DNS' --tier 'Standard'
From PowerShell
Set-AzSecurityPricing -Name 'DNS' -PricingTier 'Standard'
Default Value:
By default, Microsoft Defender for DNS is not enabled.