What is the function of Network Access Control Lists (ACLs) in AWS?

Network Access Control Lists (ACLs) play a crucial role in managing the security of your network within AWS by allowing or denying specific traffic at the subnet level. They serve as a firewall for controlling traffic in and out of one or more subnets. When a packet arrives at a subnet, the associated ACL is evaluated to determine whether it should be allowed to pass or denied based on defined rules. These rules can be set to allow or deny traffic based on specific conditions, such as IP address, protocol, and port number.

This capability to govern entry and exit points to the subnet contributes to a more secure environment, as it can help defend against unauthorized access or unwanted traffic. By applying different ACL rules to different subnets, organizations can tailor their security measures according to the specific needs and sensitivity of the data or applications running within those subnets.

The other choices do not accurately describe the purpose of Network ACLs. Managing user identities pertains to AWS Identity and Access Management (IAM), while encrypting stored data is typically handled by services like AWS Key Management Service (KMS) or S3 server-side encryption. Limiting resource visibility is more associated with IAM policies and roles rather than network-level controls, which are the domain of ACLs.