On my mac I use OS X firewall at times. But only sometimes. On my windows 2k, it doesn't have one officially but seems to have a built in one since it runs on my mac. I can't activate my OS X firewall if my win 2k is running, it comes up with a message saying another firewall is already active. (Might be some type of built-in network firewall) Sorry about the odd answer to your question. lol