Firewalls

approach to security; it helps implement a larger security policy

that defines the services and access to be permitted, and it is an imple-

mentation of that policy in terms of a network configuration, one or

more host systems and routers, and other security measures such as

advanced authentication in place of static passwords. The main pur-

pose of a firewall system is to control access to or from a protected

network (a site). It implements a network access policy by forcing

connections to pass through the firewall, where they can be examined

and evaluated.

Furthermore, a firewall system can be a router, a personal com-

puter, a host, or a collection ...