Title: Internet Firewalls - An Introduction  
Authors: Andrew T. Robinson    
File name: pubdocfirewallsRobinson_Firewalls.ps  
Filesize: 221645 bytes  

Abstract: Connecting to Internet
connection will expose some subset of your enterprise network
resources, called the zone of risk, to Internet-based attacks
from any of millions of Internet users.  One way to reduce this
exposure is to reduce the zone of risk to a small number of
extremely secure hosts.  These secure hosts are collectively
referred to as a firewall. An Internet firewall allows enterprise
network administrators to implement strict access controls,
including strong authentication methods such as token
authentication, between the Internet and the enterprise network.