getting attacked on computer

hey, i have norton and quite a few times now im getting attacked by like trojans like backdoor and subseven and some other minor things but norton blocks it but like i dont even do anything and why do i keep getting attacked?? wtf!?!?!? in my old computer it never happen to me or anything or i dont think it did so why would it start now?> i only do the same things too, but i get the ip that it is coming from and i was wondering can i do anything with that ip? like find out where it is coming from? or anything? but plz can someoen ask this to like a lot people that know about stuff because i dont think many people come to the help forum