AWS Networking Security Groups

In this post, we will see what is Security Group, what they control and how to configure security rules.

Security Groups

Security Groups are like a virtual firewall for your EC2 instance. They will control inbound and outbound traffic for your instance and they are made up of a set of inbound and outbound rules. 

Security Groups are belongs to a VPC. It is assigned at the instance level. There is no restrictions at the subnets level. Security Groups can be assigned to any number of EC2 instances which may be in same or different subnets.

Basically traffic flow will look like below. Any input traffic will come through internet gateway or vpn gateway which will pass into router and route tables to identify to which subnet it has to flow through, then it reaches the subnet and security group. 

Security Group is the final security layer for an instance before any traffic reaches the instance. SG will validate the incoming traffic using it rules defined for inbound traffic. If at all any problem occurs in accessing the instance, start your troubleshooting from SG. If it looks correct, move up to other resources in the line.

You shall have a look at the comparison made between Network Access Control List and Security Groups in my another post here.

Lets start by creating Security Group in AWS Console.

1. Login to your AWS Management Console.
2. Type EC2 in Services search box.

3. In the left side pane, under Network & Security section, click on Security Groups which will open the Security Groups home page.

        


You shall see all the security groups created in your account this page. On top right, click on Create Security Group button to start creating a new security group.