@ Draco: maybe a better solution is to get his IP and watch all incoming packets via Wireshark or anything similar, and if anything suspicious comes up, take a screenshot of the logs, save the logs and send both the logs and screenshots to his ISP and ask them to inform the local police.
I'd suggest disabling Lua or filtering any malicious activity that may occur during gameplay. One way you can do that is through server settings, at least I think there's a option to disable Lua for the server. Else for Lua filtering, create a Lua script handler to catch all bad input that may happen. How? perhaps via regular expressions or strict checks on stuff.
Think in code then realise what comes to mind, so that you'll end up with a brilliant secure server later. How's that for a solution? I personally am not very good at Lua scripting, so I don't dare to take on such Lua project but I do believe it'd be cool and nice to have protection for your own CS2D server though.
Well that just proves my point about you being a dumbass and not knowing how to use a proxy etc.
And from the thread 'Change IP' I would say you don't know how to portforward so you wont be able to ddos after either.