A network ACL (NACL) is an optional layer of security for your VPC that acts as a firewall for controlling traffic in and out of one or more subnets. You can create a network ACL and associate it with a subnet to apply rules that allow or deny traffic to or from the subnet. Network ACLs are stateless, meaning that they evaluate the source and destination IP addresses for both inbound and outbound traffic. You can also use network ACLs to block IP address ranges that are known to be malicious12.

The other options are not AWS services or tools that can be used to set up a firewall to control traffic going into and coming out of an Amazon VPC subnet. Security groups are another layer of security for your VPC that act as a firewall for your EC2 instances. Security groups are stateful, meaning that they automatically allow return traffic for allowed inbound traffic. Security groups can only filter traffic based on protocols, ports, and source or destination IP addresses, not on IP ranges3. AWS WAF is a web application firewall that helps protect your web applications from common web exploits. AWS WAF can filter web requests based on rules that you define, such as IP addresses, HTTP headers, HTTP body, or URI strings. AWS WAF does not apply to non-web traffic or to traffic within a VPC4. AWS Firewall Manager is a service that helps you centrally configure and manage firewall rules across your accounts and resources in AWS Organizations. You can use Firewall Manager to apply AWS WAF rules, AWS Network Firewall policies, and Amazon VPC security groups across your AWS accounts. AWS Firewall Manager does not provide a firewall service itself, but rather helps you manage other firewall services