Anonymous have declared they are shutting the internet down on March 31 in protest against SOPA, Wall Street, and "irresponsible leaders and the beloved bankers who are starving the world for their own selfish needs out of sheer sadistic fun."
Anonymous is not planning to kill the internet permanently, though. The group only wants to shut it down temporarily by carrying out a massive attack on thirteen root DNS servers.
“It may only last one hour, maybe more, maybe even a few days,” Anonymous said in a statement posted to Pastebin. “No matter what, it will be global. It will be known.”
By cutting off the thirteen DNS servers, Anonymous will effectively make the Internet unusable. Users will not be able to perform a domain name look-up, and will instead be greeted with an error page upon entering a familiar site's URL. Entering the direct IP address into the address bar will be the only way to reach the desired website.