Researchers at The Ohio State University in Columbus, Ohio claim to have worked out a way of spotting whether your computer has a worm, and claim they can neutralize it within seconds.

The software monitors the number of scans that machines on a network send out.  If it sends out too many scans, the administrators can take it off line and check it for viruses. A worm sends out many scans to many different destinations in a very short period of time because it looks for machines to infect. The researchers needed to calculate what was needed to stop the virus from spreading and what would stop a network from functioning. 

What surprised them was the number of IP scans a worm needed to perform to survive. In the simulations pitted against the Code Red worm, the researchers said they were able to prevent the spread of the infection to less than 150 hosts on the whole Internet, 95 percent of the time.