[dr1ftp0w3r]

Assuming you are using a Linux based server, you could try and set up some iptables rules like hit-count in each second for UDP Inbound and drop it in case limit gets exceeded, however, if they are using attack methods that are not directly with your server's network, then there isn't much that you can do, you just better ask for support at the hoster.

Sorry for my shitty english, hope this helps you.