Lol. Quick facts.
A half-decent firewall can block a DDoS attack. These are supposedly the 13 magical DNS servers of the world, how do you expect to screw with them with the lowest level of "hacking" there is?
Most important point: These servers probably receive jillions of pings a second from everyone in the entire world who happens to be looking for a web address, it's laughable that someone thinks they can shut them down with more pings. Apparently they don't, but I wouldn't be surprised if they could handle it.