Conficker.c is a worm that has infected millions of computers and is scheduled to become malicious on April Fool's day 2009. The worm, which is a self-propagating computer program, could cause widespread damage to those who do not yet have the latest Microsoft updates.
What exactly will happen on April 1, 2009 is unsure. But the possibilities range from having a person's entire hard drive wiped clean to having personal data stolen.
One of the challenges of the Conficker.c worm is that in many cases it blocks Microsoft from automatically updating and thus removing the risk.
The worm spread through websites that pretend to sell anti-virus software. These fake anti-software ads actually prompted people to download harmful software.