O'Reilly Network: Linux for Security Applications [Firewalls]Aug 12, 2000, 21:43 (4 Talkback[s])
(Other stories by David HM Spector)
"In a previous article in this series, I talked about using Linux-based systems for what could be a quasi-security purpose: network packet monitoring. In this article I go "all the way" and discuss how Linux can be used in areas where you need absolute control over what happens on a network, a firewall."
"Firewalls seem to be the stuff of legend in the IT community. Everyone has one because they're afraid of system crackers, viruses, and other nefarious things, but very few people know what a firewall is, let alone how to construct one. This article will give you a good overview of what happens under the hood, and how you might use Linux in other security applications such as penetration-testing and intrusion detection."
"In its most straightforward definition, a firewall is a process that implements a set of policies that control the flow of information between one area of interest and another. You might be wondering why I defined "firewall" in such a non-technical way. ... It turns out that the concept of a firewall in the information-management realm goes back long before the advent of computers. Looking at what a firewall does outside the context of computing can demystify what's really going on."