A firewall is a set of related programs, located at a network
gateway server, that protects the resources of a private network
from users of 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, filters all network
packets to determine whether to forward them to their intended
destination. A firewall also includes or works with a proxy
server that makes network requests on behalf of workstation
users. A firewall is often installed in a specially designated
computer separate from the rest of the network so that no
incoming request can get directly at private network resources.
There are a number of firewall screening methods. A simple one
is to screen requests to make sure