could someone explain this? thanks

hi all, I would like to ask a question and hopefully i won't get flame.
When it comes to rooting a linux/unix box. Does the attacker need to get into
the victims box first before he can exploit it? What if the attacker didn't know the
login and pw of the victims unix/linux box. Can he still root it?

*sorry for asking stupid question. I just started using freebsd and i don't wanna
expose it online if it's hackable. Don't get me wrong, i like using it but i can't risk
or even have a thought that someone from somewhere is poking my box.*

Exploitation can be things like gaining access, elevation of privileges or denial of services. I won't give away specifics, but to answer your question, no an attacker doesn't need to get into your system to exploit it. An attacker would use an exploit to gain access in the first place.

Two books I would recommend are "Hackers Beware" and "Hacking Exposed."