According to the Associated Press, South Korean hackers attacked the DNS (Domain Name System) computers that handle the .org addresses. These three computers are part of the 13 root DNS servers that map numeric IP addresses (like 216.106.112.135) to the more-familiar domain names that users have come to rely upon (like yahoo.com).
Most ISPs and large companies operate their own DNS servers, which at some point copy updated information from the root servers.
Domain names are discussed in chapter 9 of the IS 6100 text on p 341.
The attack was similar to an October 2002 attack on the 13 root DNS servers.
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