DNS root servers function as part of the Internet backbone, as explained in Wikipedia, and have come under attack a number of times in the past — although none of the attacks have ever been serious enough to severely hamper the performance of the Internet.
In response to some of the common misconceptions about the physical location and total number of DNS root servers in the world, Patrik Faltstrom has put together a visual map on Google, pin-pointing the approximate location of each server around the world. (Note: The map may be incomplete and Patrik is updating it as he gathers more input.)
|Cybersquatting||Policy & Regulation|
|DNS Security||Registry Services|
|IP Addressing||White Space|
Minds + Machines