The best firewall is really a broad question. If this is a business it will be different from a home firewall. You can get by with an IPtables firewall. This is the standard for linux systems. I use it, it currently protects www.pureescape.net , it works great. The rules are very flexible and you really have total control of what's allowed and not allowed to go over the wire. It's an easy firewall to learn, with lots of configuration tools readily available, plenty of documentation and you can even find already hardened scripts that you can customize. So, I'd strongly recommend it for your small to mid size business or personal setup.

For a big business, I'd look into some Cisco products. Nobody knows IP like Cisco, they'll set you up straight.


--PuRe