The Conficker worm is scheduled to activate on April 1, and the unanswered question is: Will it prove to be the world’s biggest April Fool’s joke or is it the information age equivalent of Herman Kahn’s legendary 1962 treatise about nuclear war, “Thinking About the Unthinkable”?
Conficker is a program that is spread by exploiting several weaknesses in Microsoft’s Windows operating system. Various versions of the software have spread widely around the globe since October, mostly outside the United States because there are more computers overseas running unpatched, pirated Windows. (The program does not infect Macintosh or Linux-based computers.)
An estimated 12 million or more machines have been infected. However, many have also been disinfected, so a precise census is difficult to obtain.
It is possible to detect and remove Conficker using commercial antivirus tools offered by many companies. However, the most recent version of the program has a significantly improved capacity to remove commercial antivirus software and to turn off Microsoft’s security update service. It can also block communications with Web services provided by security companies to update their products. It even systematically opens holes in firewalls in an effort to improve its communication with other infected computers.
More info about Conficker @ Wikipedia