dos spoofed prevent?

[gamemann]

Hello, my ze server keeps getting attacked. It's kinda getting annoying now. We get a high player count then boom dos. My host has confirmed it's a 14 mbit dos attack with a spoofed ip. I have daf(sourceop), query cache metamod addon. None of them are working at all. This attack is really deadly, alot of people say it's weak and probably is, but i can't even start my server for 4 hours until it's done. If someone can make a plugin for me, then i will give you admin on my group and maybe even pay you. But it has to work. And my host said we aren't switching to linux and he can't stop the attack.
Thanks,
Gamemann