Firewall

Hardware or software used for network security. A firewall can be implemented as a router that filters packets, or may consist of a combination of routers, proxy servers, and other devices. Firewalls are widely used to separate a companyÆs public servers from its internal network, and to give users relatively secure access to the Internet. They are also used to secure internal network segments. For example, a Human Resources subnet may be isolated from the research or accounting subnetwork to prevent unauthorized access from within.