INTRODUCTION TO SECURITY GROUP

Security Group are the network security in AWS.It control how traffic is allowed in or out of our EC2 instances.
Security Group contain only allow rules.Security Group can reference by IP or by Security Group.

NOTE: Security Group is a instance firewall.

NOTE : Security Group is Stateful. Stateful means if a request is allowed in inbound, the response for the request is automatically allowed to outbound this is called Stateful.

Security Group regulates:

1. Access to ports.
2. Authorised IP ranges -IPV4 and IPV6 3.Control of inbound network that means from other to the instance. 4.Control of outbound network that means from instance to the other.

About Security Group want to know more:
. Can be attached to multiple instances.(That instances have multiple security groups too)
. Locked down to region / VPC Combination (We have to create security group for region as well as VPC).
. If the traffic is blocked the EC2 instance won't see it.
. It is good to maintain one separate security group for SSH access.
. If our application is not accessible (timeout) then it will security group issue.
. If our application is "connection refused" error then it must be application error or its not launched.
. All inbound traffic is blocked by default.
. All outbound traffic is authorised by default.

In Security Group we want to know more:

Classic Ports:

1. 22 - SSH (Secure Shell) - Login to Linux Instance.
2. 21 - FTP (File Transfer Protocol) - We upload files into a file share.
3. 22 - SFTP (Secure File Transfer Protocol) - We will upload files using SSH because it is going to be a secure file transfer protocol.
4. 80 - HTTP (Hyper Text Transfer Protocol) - It is used to access unsecured websites.
5. 443 - HTTPS - It is used to access secured websites.
6. 3389 - RDP (Remote Desktop Protocol) - It is used to Login into a Windows Instance.