Description:

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.


Audit:

From Azure Portal

1. Go to Microsoft Defender for Cloud

2. Select Environment Settings blade

3. Click on the subscription name

4. Select the Defender plans blade

5. Ensure Status is set to On for DNS.

From Azure CLI

Ensure the output of the below command is Standard

az security pricing show -n 'DNS' --query 'PrincingTier'

From PowerShell

Get-AzSecurityPricing --Name 'DNS' | Select-Object Name,PricingTier

Ensure output of PricingTier is Standard


Remediation:

From Azure Portal

1. Go to Microsoft Defender for Cloud.

2. Select Environment Settings blade.

3. Click on the subscription name.

4. Select the Defender plans blade.

5. Select On under Status for DNS.

6. Select Save.


From Powershell

Enable Standard pricing tier for DNS:

az security pricing create -n 'DNS' --tier 'Standard'

From PowerShell

Enable Standard pricing tier for DNS:
Set-AzSecurityPricing -Name 'DNS' -PricingTier 'Standard'

Default Value:

By default, Microsoft Defender for DNS is not enabled.


References:

1. https://azure.microsoft.com/en-us/pricing/details/defender-for-cloud/

2. https://docs.microsoft.com/en-us/security/benchmark/azure/baselines/dnssecurity-baseline

3. https://docs.microsoft.com/en-us/azure/defender-for-cloud/defender-for-dnsalerts

4. https://docs.microsoft.com/en-us/azure/defender-for-cloud/enable-enhancedsecurity

5. https://docs.microsoft.com/en-us/azure/defender-for-cloud/alerts-overview

6. https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3- network-security#ns-10-ensure-domain-name-system-dns-security

7. https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3- logging-threat-detection#lt-1-enable-threat-detection-capabilities