Which AWS service or feature is associated with a subnet in a VPC and is...

 Network ACLs (network access control lists) are an optional layer of security for your VPC that act as a firewall for controlling traffic in and out of one or more subnets. You can use network ACLs to allow or deny traffic based on protocol, port, or source and destination IP address. Network ACLs are stateless, meaning that they do not track the traffic that flows through them. Therefore, you must create rules for both inbound and outbound traffic.