What is a network access control list (ACL) in AWS?

A network access control list (ACL) in AWS is fundamentally a set of rules that dictate the allowed or denied traffic to and from resources in a Virtual Private Cloud (VPC). These rules are evaluated in order, and they can be used to control both inbound and outbound traffic for subnets within the VPC.

When configuring an ACL, you can specify the source and destination IP addresses, protocols, and port numbers for network traffic, thus providing a fine-grained level of control over your network security. This allows you to manage and filter traffic to help secure your AWS resources effectively.

The other options do not accurately represent the function of a network ACL. A virtual private cloud refers to the isolated network environment for your AWS resources, not to traffic control specifically. A type of storage solution typically refers to services like Amazon S3 or EBS and does not relate to controlling network traffic. A monitoring tool for applications would involve services like Amazon CloudWatch or AWS X-Ray, which focus on tracking application performance rather than regulating network access.