Azure DDoS Protection Preview will help protect your applications from being impacted by distributed denial of service (DDoS) attacks at OSI layers 3-7. This service will monitor the public IP addresses of your resources within Azure, learn an application’s normal traffic patterns, and instantly mitigate an attack when it’s detected. When you subscribe to this service, you will also receive advanced telemetry and alerts related to attacks carried out against your application. During preview, you won't incur any cost for using the service. For more information, please visit the Azure DDoS Protection page.
Source: Azure Roadmap