The current threat level from terrorism in the UK and many other countries is set to severe, and police and security forces acknowledge that their jobs are being made much harder because today's terrorists have at their disposal a range of communications and social network tools to help them to form alliances, attract new recruits and orchestrate terror campaigns. But, the associations that terrorists make through these channels can also help to identify them, if police are able to screen this sort of data routinely. Most people, though, are justifiably concerned about privacy. Now Michael Kearns, from the University of Pennsylvania, has come up with a way to keep honest data safe yet still enable security forces to track down the bad guys: you add some noise to the information, as he explained to naked scientist Connie Orbach...