How do Anti-DDoS systems work?

Question

DDoS Protection

Hello, it became very interesting how various Anti-DDoS systems work?
For example, how does Anti-DDoS from CloudFlare work (there, it seems, protection at the DNS level)?
There is also a site - react.su, which also protects against DDoS (actually, no, a large site was recently put up that was protected by this system).
And what levels of protection against DDoS attacks are there if you connect services like CloudFlare?

Answer 1

Anti-DDoS from CloudFlare (there, like, protection at the DNS level)?

Your traffic is being proxied.
Read about levels of DDoS attacks.