What is an access control list (ACL)?

An access control list (ACL) serves as a set of rules that determines which users or systems are allowed to access specific resources and what actions they can perform. In the context of network security, ACLs are extensively used to filter incoming and outgoing network traffic. This mechanism allows administrators to permit or deny traffic based on various parameters like IP addresses, protocols, or port numbers. By defining these rules within the ACL, network security can be enhanced, protecting the network from unauthorized access and other security threats.

The role of ACLs is particularly vital in routing and firewall configurations, where they help manage the flow of data based on defined security policies. This direct control over network traffic helps maintain the integrity and confidentiality of data within the network environment. Other choices do not encompass the full scope and purpose of an ACL accurately, as they refer to different concepts not related to this specific functionality in network management.