We talked briefly about security groups in the previous chapter, but in this section, we will be looking at them in a bit more in detail. Security Groups are simple, yet powerful ways using which you can secure your entire EC2 environment. You can use Security Groups to restrict and filter out both the ingress and egress traffic of an instance using a set of firewall rules. Each rule can allow traffic based on a particular protocol—TCP or UDP, based on a particular port—such as 22 for SSH, or even based on individual source and destination IP addresses. This provides you with a lot of control and flexibility in terms of designing a secure environment for your instances to run from.
Let's look at how you can edit an existing Security Group using the EC2 dashboard.
From the EC2 dashboard, select the Security Groups option located under the Network & Security section as shown here:
This will display a list of currently created and in use Security Groups present...