Security Group
#15 · Level 1 · Core services · Networking basicsConcept
Section titled “Concept”A Security Group is each server’s own firewall, deciding which traffic can come in and go out. It is attached directly to a resource such as an EC2 instance, not to a subnet. You can only write allow rules in it — anything not allowed is blocked automatically. A Security Group is stateful, which means that if a request is allowed in, its response can go back out automatically. You can attach more than one Security Group to a resource.
Simple example
Section titled “Simple example”The guard at a flat’s door, who has a list of people allowed in. If your name is on the list, you can enter; if not, you can’t.
Why it’s needed
Section titled “Why it’s needed”If everyone could come in from every direction, attackers could easily get in. Only the doors you need should be open.
Where it’s used
Section titled “Where it’s used”A web server’s Security Group opens only the door for viewing the website. A database’s Security Group lets in only the web server, and nobody else.
Azure equivalent
Section titled “Azure equivalent”Network Security Group (NSG)
Related
Section titled “Related”Network ACL · Amazon VPC · Amazon EC2
Learn more
Section titled “Learn more”For details and the latest information, see the official documentation: