Used to list accounts having access not only to the computer system in general but also to the information resources to which that list pertains. For example, a system administrator can configure firewalls to allow access to different parts of the computer network for different users. The ACL, therefore, would include the list of Internet Protocol (IP) Addresses having authorized access to various ports and information systems through the firewall.

An additional layer of security, particularly for Web applications, is provided by reverse proxy servers—technical systems through which requests to a Web applications flow before they get to the application servers. These systems also rely heavily on ACLs to control which IP address ranges are allowed to connect to the service.

The term is also used to describe the security policies in a computer file system.

See Also: Administrator; Firewall; Internet Protocol (IP); IP Addresses; Network; Port and Port Numbers.