add Azure DDoS

Author: msmimart

articles/active-directory/manage-apps/application-proxy-security.md

@@ -12,7 +12,7 @@ ms.workload: identity
 ms.tgt_pltfrm: na
 ms.devlang: na
 ms.topic: conceptual
-ms.date: 09/08/2017
+ms.date: 03/13/2020
 ms.author: mimart
 ms.reviewer: japere
 ms.custom: it-pro
@@ -77,13 +77,15 @@ Unpatched software still accounts for a large number of attacks. Azure AD Applic
 
 To improve the security of applications published by Azure AD Application Proxy, we block web crawler robots from indexing and archiving your applications. Each time a web crawler robot tries to retrieve the robot's settings for a published app, Application Proxy replies with a robots.txt file that includes `User-agent: * Disallow: /`.
 
-### DDOS prevention
+### DDoS prevention
 
-Applications published through Application Proxy are protected against Distributed Denial of Service (DDOS) attacks.
+Applications published through Application Proxy are protected against Distributed Denial of Service (DDoS) attacks. The Application Proxy service monitors the amount of traffic attempting to reach your applications and network. If the number of devices requesting remote access to your applications spikes, Microsoft throttles access to your network.
 
-The Application Proxy service monitors the amount of traffic attempting to reach your applications and network. If the number of devices requesting remote access to your applications spikes, Microsoft throttles access to your network. 
+Microsoft watches traffic patterns for individual applications and for your subscription as a whole. If one application receives higher than normal requests, then requests to access that application are denied for a short period of time. If you receive higher than normal requests across your whole subscription, then requests to access any of your apps are denied. This preventative measure keeps your application servers from being overloaded by remote access requests, so that your on-premises users can keep accessing their apps.
 
-Microsoft watches traffic patterns for individual applications and for your subscription as a whole. If one application receives higher than normal requests, then requests to access that application are denied for a short period of time. If you receive higher than normal requests across your whole subscription, then requests to access any of your apps are denied. This preventative measure keeps your application servers from being overloaded by remote access requests, so that your on-premises users can keep accessing their apps. 
+#### Azure DDoS protection service
+
+**Azure DDoS protection** is a service offered with the Azure platform to protect your Azure resources from denial of service (DoS) attacks. The **Basic** service tier is automatically enabled, providing always-on traffic monitoring and real-time mitigation of common network-level attacks. A **Standard** tier is also available, offering additional mitigation capabilities that are tuned specifically to Azure Virtual Network resources. For details, see [Azure DDoS Protection Standard overview](https://docs.microsoft.com/azure/virtual-network/ddos-protection-overview).
 
 ## Under the hood