Well "IF" a "hacker" tries to get into your system he WILL . The only thing you can do about it is catch him before he can do any damage. You might want to get a good virus scan and a good firewall. If you firewall catches somebody trying to get into your system report it to your isp or their isp. And if a "hacker" tries to get into your system its probably because you post questions with NO DETAIL........ Its like asking what do i do if a person breaks into my house?
(In case you don't know the answer You call the cops.)
Just my two cents,