On October 20, Duqu went dark, and no one is sure why. This computer worm has spread far and wide and is very similar to a more famous computer work. Stuxnet hit the news before its less well-known cousin. Duqu appears to be preparing for an even broader attack on industrial targets. Duqu first showed up two years ago, but the October event saw all known Duqu servers (computers copies of Duqu sent information back to) mysteriously erasing all evidence of Duqu and, as far as anyone could tell, Duqu had shut down. But security experts believe that the Duqu operators were simply seeking to hide their activities from the Internet security experts who have been trying to track this new worm.
Stuxnet, a computer worm (a computer program that constantly tries to copy itself to other computers) showed up two years ago. It was designed as a weapons grade cyber weapon, and was designed to damage Iran's nuclear weapons manufacturing facilities. It succeeded.
But now Duqu, a Stuxnet variant, has been discovered, and it appears to have been created by the same group that designed Stuxnet, and released about the same time. Duqu, however, does not attack. Rather it was being used to probe industrial computer systems and send information about how these systems are built and operate, to someone. Duqu was revealed to the public earlier this year, and further searching revealed that Duqu was all over the place.