SD has written
Quite effective way to protect yourself from attacks like these is to ban specific (presumably hacker's) IP address
Most ISPs provide dynamic IP addresses, and most of those provide it by default. Simply restarting your DSL router will give you a change in IP in these circumstances. IP bans work well where there are extremely large numbers of internet users, which would acount for a large portion of Europe, ( I know several ISPs in Britain at least give static IP's to their customer by default. ) but if you try to do this to people from countries that are in South America an most of Africa, you won't succeed.
EDIT: One solution to the problem would be to log packet data and then look at the series of packets coming in when the server is crashed, then monitor the incoming packet traffic to your server port and reject packets from an IP address if there are a large number ( say, 1000 or maybe less depending on how many packets are needed before the server crashes ) of that type of packet from said IP address.
An example, if you recieve 1500 packets of this structure ( note: not actual packets from CS2D ):
1
Message Number = 0; content = 0x61 0x6F 0x42