DDOS Protecting a Game Server?

The fact that it's a non-famous system protects you from DDoS attacks.
DDoS = Distributed Denial of Service.

They take a botnet of hundreds or thousands of machines scattered around the world, all trying to access the system at the same time; that's the "Distributed" part.

No magic, just a brute-force overload where all the converging data streams come together; that's the denial of service part, the last part of the connection is just too congested to do much.

There are few botnets and the controllers don't use them for trivial stuff like messing up someone game server…

There are other types of attack that may cause hiccoughs but generally a good branded router with a properly set up firewall can handle most of those.

All you can really do is use a good firewall that focuses on DDOS attacks. Other than that you can buy a ton of hardware, but I doubt you have millions of dollars for that.