Linux.com: Introduction to FirewallsNov 21, 2000, 21:09 (0 Talkback[s])
(Other stories by Brad Marshall)
"In this article I cover some of the design decisions that have to be made before creating a firewall, from architecture to various decisions that should be made."
"A firewall is a device that separates and protects your network, in most cases, from the Internet. It can restrict traffic to only what is acceptable and allows monitoring so you can see what is happening. Firewalls enforce a security policy by establishing a single point for security decisions to be made. They also limit exposure to the Internet, and allow you to log traffic."
"Firewalls can't do many things. They can't protect against malicious insiders. If someone wants to copy your data onto a disk and walk out with it, the best firewall known can do nothing about it. Similarly, firewalls can't protect connections that don't pass through them. If someone has a dialout modem, there is nothing the firewall can do to protect this connection. And, perhaps most important, firewalls can't set themselves up. All firewalls need some measure of configuration, and all networks are slightly different. A misconfigured firewall may give you an illusion of security, which might entice you to act as if you're protected when you really aren't."