First off, this isn’t a hoax. There’s a warning about this on the FBI Web site (see article links). You can also Google “Internet Doomsday” and you’ll find plenty of other links from reputable sources.
The FBI is working with foreign governments to control a computer bug that could keep you from connecting to the internet as of July 9, 2012. You have until then to check your computer and download the free fix if it’s infected (via Living on the Cheap).