Linux.com: A Linux Firewall Primer

“You’ve heard the familiar arguments: commercial firewall
products are overpriced; proprietary firewall code leaves you at
the mercy of a vendor’s timetable in the event of a security hole;
the cost of underlying hardware/software platform for Windows is
high and puts you on an escalating upgrade path. As your company’s
key IT decision-maker you can’t afford to spend money needlessly
nor ignore even temporary security issues, so you’re thinking
seriously about deploying a Linux-based firewall solution. What do
you need to know?

“Network security is a broad topic, and while a good firewall is
an essential part of network security, it does not work in
isolation. A secure system also requires effective monitoring and
intrusion detection, as well as a ‘respond and restore’ plan in the
event of a security breach. We’ll be restricting our discussion to
firewalls, but keep in mind that your firewall plan must coexist
with your other security measures…”