[tlug] Does Linux need, or have, a firewall?

[Dave M G <martin@example.com>]

TLUG,

    My understanding of Linux was that it did not need a firewall as a 
seperate program, the same way that say, Windows uses ZoneAlarm or 
similar firewall applications. This was because port blocking and other 
firewall tasks were built into the way the OS operates.

    First question, is the preceeding paragraph true?

    I've been having trouble setting up ports to be "open", or mapped, 
to certain P2P applications. With help from the Tokyo PC Users group, 
I'm reasonably certain I've done all I can with my router (and it's DHCP 
server) to map certain ports to my machine. But they remain blocked, and 
I'm reasonably certain it's at the OS level, I'm just not sure what, 
exactly, the OS is doing.

    After some Google searching and web surfing, I eventually decided to 
try an application called Firestarter. This is supposed to be a GUI for 
managing Linux's firewall settings. Unless I'm wrong about what I said 
above and it's actually creating a firewall instead of merely managing 
settings.

    In any case, with Firestarter I attempted to map some ports to my 
computer's IP address, and unblock some connections. But I'm still not 
getting the throughput that I hoped for.

    Second question, am I barking up the wrong tree? If I want to map 
ports on the OS side, is Firestarter the way to go? Is there somewhere 
else I should be dealing with this?

    Any help in this matter would be greatly appreciated.

    Thank you.

--
Dave M G