A security group is a firewall for EC2 instances. It controls inbound and outbound network traffic. By default, all inbound traffic is blocked and all outbound traffic is allowed. Security groups can be attached to multiple instances and an instance can have multiple security groups. Security groups are locked down to your region/VPC combination. Good to know: - Security groups live outside the EC2 instance. - If traffic is blocked, the EC2 instance will not even see it. - It is good to maintain one separate security group just for SSH access. - By default, all inbound traffic is blocked and all outbound traffic is allowed. - You can reference security groups from other security groups.
What are security groups?
What happens if you try to connect to an EC2 instance that is not authorized on your security group?
What is the default setting for inbound traffic on security groups?