Nameservers, which store the records that connect domain names with specific IP addresses, are attractive targets for hackers because they control the availability of large numbers of web sites. In 2002 the Internet’s root nameserver system came under attack, with the DDoS causing network congestion but only minor performance problems for the DNS system, which a subsequent analysis noted is “massively overprovisioned to make it robust against attacks or network failures.”
In the wake of that attack, most major registrars have robust infrasturcture to defend against DDoS attacks. It’s not immediately clear whether the problems at Joker.com are related to the specifics of its DDoS defenses or the sheer volume of the attack. In recent weeks some Internet security groups have warned of the dangers posed by DNS recursion attacks, which can use the nameserver system to amplify a DDoS launched by a bot network.