There is no problem asking a question about your mac as long as it related
directly to ubuntu - which would assume that you are networking with a ubuntu,
installing it on your mac - etc.

First off lets start with your security problems. If you are NOT using a
firewall and then you are opened to being hacked. So, use a firewall and virus
protection.

Second, a mac is not fool-proof. As Apple has built on top of a solid system,
they have created more problems.

I just checked on this site you mentioned for a pc and its down as they are
moving. But I dont personally know anything about them. You can purchase a dell
with ubuntu on it or even better, purchase a barbones kit and install ubuntu on
there.

As you said, an computer can by hacked. It all depends on how you set it up.
What ports you open, etc.

As for someone tracking you, that is pretty scary. But consider this: even if
someone knows my ip address, I have a firewall on my modem and a firewall on my
computer. This gets into a whole area that is difficult to discuss here but, if
someone hacked your windows pc and then your apple pc, I have to think right off
you dont have a firewall up and second, you might be exposing yourself by using
programs that are known to have problems.

To answer your overall question: I have ubuntu setup just as a fresh install and
I install firestarter. I can see people pinging ports like crazy but I have
little to worry about since they are all closed.