A firewall is a set of related programs, located at a network gateway server, that protects
the resources of a private network from users from other networks. (The term also implies the
security policy that is used with the programs.) An enterprise with an intranet
that allows its workers access to the wider Internet installs a firewall to prevent outsiders from
accessing its own private data resources and for controlling what outside resources its own users
have access to.
Basically, a firewall, working closely with a router
program,...
