Perimeter Defense; The Firewall

Abstract

As companies increasingly build private networks and connect them onto the Internet, securing such private networks has become a great concern. These networks are facing threats from two fronts: the external Internet and the users from within the company network. This requires security protocols that will effectively deal with these two fronts by first restricting access to the network from outside and controlling access between subnets from within. Ideal protocols to do such tasks are found in firewalls. A firewall is hardware, software, or a combination of both that monitors and filters traffic packets that attempt to either enter or leave the protected private network. It is a tool that separates a protected network or part of a network, and now increasingly a user’s personal computer (PC), from an unprotected network—the “bad network,” like the Internet.