AWS Network ACL
AWS Network ACL (Access Control List) is a stateless firewall service in Amazon Web Services that controls inbound and outbound traffic at the subnet level in a VPC (Virtual Private Cloud). It operates as a numbered list of rules evaluated in order to allow or deny traffic based on IP addresses, ports, and protocols. Unlike security groups, Network ACLs are stateless, meaning return traffic must be explicitly allowed by rules.
Developers should learn AWS Network ACL when designing secure AWS architectures, particularly for implementing network segmentation, compliance requirements, or controlling traffic between subnets in a VPC. It's essential for scenarios like isolating public and private subnets, blocking specific IP ranges, or enforcing strict network policies in multi-tier applications, providing an additional layer of security beyond security groups.