DDoS causing Server to Crash, Asking for Mod

[fatal1980]

I think you need to identify the attack first before you try blocking it. Are you sure its not just a simple syn flood attack? Which is rather simple to block. Even then if they're making multiple connections to your server per second you can block them using iptables.

iptables -A BADGUY -p tcp --syn --dport 80 -m recent --name dos --update --seconds 10 --hitcount 16 -j DROP