What do Network Access Control Lists (NACLs) provide in AWS?

Network Access Control Lists (NACLs) in AWS are designed to operate at the subnet level, providing a layer of security by allowing or denying inbound and outbound traffic based on rules that you define. This is crucial for managing access to resources within a Virtual Private Cloud (VPC).

NACLs are stateless, meaning that rules must be explicitly defined for both incoming and outgoing traffic. For example, if an incoming rule allows traffic from a specific IP address, you must also have an outgoing rule that permits the response traffic back to that IP. This granular control allows you to better manage security and traffic flow at the subnet level.

By filtering traffic at this level, NACLs help to enforce a security posture across all resources within the specific subnet, acting as a first line of defense before traffic reaches the instances. This capability is especially useful in environments where multiple subnets may have different security requirements or access policies.

In contrast, other options focus on functionalities that do not pertain to the role of NACLs. For instance, monitoring at the instance level refers more to security groups, which are another form of network security that operates at the instance level, while detailed analytics on VPC performance and backup solutions pertain to different areas of