How to protect the server from UDP flooding to the game server?

Question

linux

The thing is, there is a server there, some kind of port 2500, I noticed that the server literally immediately goes to bed at DoSe on UDP flood. (And yes, I’m sure that I didn’t fill my Internet band, I tested with the help of my VPS).
How can you solve this problem so that you can play, and such ddosers are thrown away?
On different OS Windows/Linux?

Answer 1

Linux:
Calculate the average traffic from a normal user, packets per minute. After adding a good margin, you limit the number of packets per second per ip address in iptables.
In addition, if the game server logs errors when receiving flood packets, you can add log monitoring via fail2ban, sending ban those ip-addresses that cause a lot of such errors