Edit.

Author: jimdial

articles/virtual-network/security-overview.md

@@ -1,6 +1,6 @@
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 title: Azure security groups overview | Microsoft Docs
-description: Learn about network and application security groups for controlling the flow of network traffic between Azure resources.
+description: Learn about network and application security groups. Security groups help you filter network traffic between Azure resources.
 services: virtual-network
 documentationcenter: na
 author: jimdial
@@ -17,13 +17,13 @@ ms.date: 09/19/2017
 ms.author: jdial
 
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-# Security groups
+# Network and application security groups
 
 You can limit network traffic to resources in a virtual network using network and application security groups. A network security group contains a list of security rules that allow or deny inbound or outbound network traffic based on source or destination IP address, port, and protocol. An application security group allows you to group together virtual machines that have similar functions, such as web servers. You can specify an application security group as the source or destination in a network security group rule.
 
 ## Network security groups
 
-Each network interface has zero, or one, associated network security group. Each network interface exists in a [virtual network](virtual-networks-overview.md) subnet. A subnet can also have zero, or one, associated network security group. 
+Each network interface has zero, or one, associated network security group. Each network interface exists in a [virtual network](virtual-networks-overview.md) subnet. A subnet can also have zero, or one, associated network security group.
 
 When applied to a subnet, security rules are applied to all resources in the subnet. In addition to network interfaces, you may have instances of other Azure services such as HDInsight, Virtual Machine Scale Sets, and Application Service Environments deployed in the subnet.