VPC Security—Security Groups and NACLs
Explore how AWS VPC security works by understanding Security Groups and Network ACLs. Learn to configure stateful Security Groups for individual resources and stateless NACLs for subnet-level filtering. Discover their differences and how they work together to control inbound and outbound traffic, ensuring secure network traffic management in your AWS cloud environment.
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When you launch an EC2 instance as a web server, it is locked down by default. The instance won’t respond to traffic unless rules are added to allow it. This is intentional: AWS attaches a Security Group, which functions as a virtual firewall around the instance.
Unlike traditional firewalls, Security Groups are stateful. If we allow inbound traffic on port 443 (HTTPS), the corresponding response traffic is automatically allowed, even if no explicit outbound rule exists. Security Groups operate at the ENI (elastic network interface) level, meaning they apply directly to EC2, Lambda (in VPC mode), RDS, and other services with network interfaces. ...