One of the biggest Distributed denial of service attacks recorded to date was to CloudFlare’s data centers in the UK. And probably bitcoin.
CloudFlare CEO Matthew Prince said on twitter that the traffic generated by the attack was about 400Gbps. The DDoS exploited the ntp protocol running on udp port 123. The attack was cleaverly exicuted by the attacker/s sending only a few packets with a spoofed source address to a “reflector” and that device would then generate traffic to its target. Large amounts of traffic.
I personally think the target was Bitcoin. There are many bitcoin servers hosted with cloudflare. The DDoS was most likely not intended to bring down cloudflare, as cloudflare boasts about their great DDoS mittigation technologies. With the recently exploited vulnerability with some bitcoin transacions, it would be rather easy for those exploits to be taken advantage of while everything else is slow and all the attention is focused on the DDoS.
Some more info and reading about Cloudflare DDos and Bitcoin here: