Computer viruses flourish on the Internet. Every time a file is downloaded, there is a chance that a virus is taking a ride. Some viruses even hide in e-mail attachments. Researchers at IBM are working to block these destructive programmes. Steve White, a senior virus researcher, and his colleague Gregory Sorkin have developed a neural network to analyse computer viruses. They trained the networks to recognise the common data structures, tasks and combinations of instructions shared by fragments from different species. The results have surprised White's professional virus-hunter colleagues. The programme has already found six viruses that no one had earlier identified.