Conficker has been infecting Windows machines since October, but in recent weeks it has been getting a lot of attention as a newer version of the worm, Conficker.C, has updated the way it looks for instructions, making it much harder to stop.

Over the past weekend, Conficker infected nearly 800 PCs at the University of Utah's Health Sciences Center. IT staff there think it might have gotten on the network via an infected thumb drive. Once installed on one PC, Conficker is very effective at seeking out other unpatched Windows machines to spread.

Users who wonder if they're infected by the worm can try out this developed by SecureWorks.