“Many years ago, large, brick walls were erected between
buildings and wood houses, so that if a fire broke out, it wouldn’t
spread. Naturally, these walls were called firewalls.“
“The Internet is said to have connected somewhere around 50,000
networks, and over 200 million hosts. Unfortunately, some of these
hosts are bound to have malicious users, or crackers. These days, a
virtual firewall of sorts is constructed between the local network
and the Internet to prevent the “fire” (the crackers) from
spreading into the “building” (the local area network).”
“The firewall is typically the first line of defense for any
Internet-connected network. Unfortunately, many network
administrators take firewalls for granted, and they become not only
their first but their last line of defense. It can’t be stressed
enough that firewalls are not the be all and end all of network
security. While a well-constructed firewall policy will greatly
reduce your susceptibility to attack, it will not (and cannot)
completely eliminate it.”