What methods (services) are used incorrectly in a ddos ​​attack with UDP amplification?

Question

Computer networks

I was once asked such a question, a bit illogical, but I'm not a professional and I don't know the answer, although for development purposes it also became interesting!
What methods (services) are used incorrectly in a ddos ​​attack with UDP amplification?
I could translate sloppily from English, so here's what it's like in the original: What are the common services being misused in UDP amplification DDOS attacks?

Answer 1

It's just that UDP is a very fast sending of packets, lately, usually everyone who has their own servers or sites closes UDP tightly.
But from the correct DDoS attacks and closing UDP does not save.
If you use UDP and you are attacked by competitors, I can offer our service to protect against DDoS attacks.