Counter-attack

Well some ninny has been attacking my system again! My firewall keeps stopping them, but its really slowing my system down ('cos of all the attack alert messages), so I was wondering is there a program (freeware of course!) that I can have onboard to send counter-attacks back at the attackers machine and bring their PC to a grinding halt, just I'm getting v.fed-up with these cyber-vandals 
Cheers
Ozzy

Cheers
Ozzy