Security Groups
ELI5 — The Vibe Check
Security groups are virtual firewalls that wrap around your cloud instances like a force field. You define which traffic is allowed in (ingress) and out (egress), and everything else is blocked. They're stateful — if you allow traffic in, the response automatically goes out. Think of them as the 'allowed list' for your server's network connections.
Real Talk
Security groups act as stateful, instance-level virtual firewalls in cloud environments (AWS, GCP, Azure). Rules specify allowed traffic by protocol, port, and source/destination (IP ranges or other security groups). They're stateful — return traffic for allowed inbound rules is automatically permitted. Default behavior denies all inbound and allows all outbound traffic.
When You'll Hear This
"The web server security group allows 80 and 443 from anywhere, SSH from the VPN only." / "Reference the API security group as the source — don't hardcode IPs."
Related Terms
Cloud Firewall
A cloud firewall is a virtual bouncer that controls what traffic can enter and leave your cloud resources.
Firewall
A firewall is the bouncer at your network's door. It checks every incoming and outgoing connection against a list of rules and blocks anything suspicious.
IAM (Identity and Access Management)
IAM is the permission system for AWS. It controls who (users, roles, services) can do what (read S3, start EC2, invoke Lambda) on which resources.
Network Policy
Network policies in Kubernetes are like firewall rules for pods.
VPC (Virtual Private Cloud)
A VPC is your own private section of the AWS cloud — like a gated neighborhood where your servers live.