zone alarm, how do i know if im being hacked?!?

ok i have zone alarm ver 3.7.143, and i have the security settings on high, and i blocked the trusted and internet zone servers. since install i have 174 blocked intrustions, 1 of them high rated, and blocked 42 access attempts. how am i supposed to know if its a hacker thats trying to hack my comp. sometimes i get alerts from the same ip address like xxx.xxx.x.xxx:1057 or something. is there any way to tell if its a hacker or not.. PLEASE HELP i need to know