From my understanding the top 21 block producers have very beefy systems and it would be very hard to ddos them. Is this true? What protections do they have from a ddos happening?
Most block producer list and describe the hardware they use on their website:
They also often have multiple server in different location, for example a block producer located in Beijing China can have other server in Pekin or even another continent like Spain, and also I suppose they use the standard anti ddos protection https://en.wikipedia.org/wiki/DDoS_mitigation