What feature differentiates NACLs from Security Groups in AWS?

NACLs, or Network Access Control Lists, are distinguished from Security Groups primarily by their stateless nature. This means that when a request is made from an instance, the response must be explicitly allowed by NACL rules. If an inbound rule permits traffic, there must also be a corresponding outbound rule for the return traffic, as the NACL does not remember the state of the connection.

On the other hand, Security Groups are stateful, meaning that if an incoming request is allowed, the outbound response is automatically allowed regardless of outbound rules, as the connection state is tracked. This fundamental difference influences how traffic is managed and controlled within AWS networks.

Understanding this distinction is crucial for effectively managing security and traffic flow in any AWS environment. It is essential for designing network architectures that cater to specific security needs.