Spy games

to track. If the same face is viewed from a different angle, or under different lighting conditions, the system can recognise the similarity, even if it doesn't get an exact match. When the operator searches for appearances of a particular individual, the system also displays close matches, which can be easily sorted through by hand.

That might not be as sexy as automatically getting an exact ID of everyone attending a World Cup match, but the difference is that it actually works, says Ross. "Face recognition is not perfect, but in the past, people have tried to employ it as though it were," he says. "We use it like Google, it lists the matches in order of confidence level. If the correct match turns out to be the sixth on the list, that's still a good result."

Hotels are using the system to monitor access to the building, for example displaying a mug shot of any person walking around, which makes it easier for security guards to spot known criminals. Similarly, banks are using it to help identify fraudsters against a watch list. In offices, the system can keep an eye on employees, which could come in handy when something goes wrong, Ross says.

"If you find out somebody is stealing data from the server room, you don't just want a picture of the guy who took the box, you want to be able to look back at who he's been talking to, and find out who his confederates were," he says.

Video systems can prove useful in criminal and corporate investigations, as was shown after the 7 July attacks in London, points out Heiser. But so far the lack of workable analytic technology has held them back. "Knowledge is just data until it's searchable and retrievable," he says. "Whether or not this technology actually works, it's the sort of thing you need to be able to do for surveillance to reach its full potential."

Other start-ups are adding further cleverness into the system. Vidient Systems, for instance, uses technology originally developed by NEC for use in broadcast video to recognise particular behaviours, such as multiple vehicles piggy-backing through a check point. "When you integrate video with your access card reader system or biometric signature, and fuse that identity with behaviour, you end up with a richer sense of what's going on," says Vidient president and chief executive Brooks McChesney.

Imprivata's OneSign adds another layer of information from a company's physical authentication system. This can be tied to network access, helping companies to enforce their badging-in policies, for instance, or locking former employees out of the network as soon as their key-card privileges are revoked. It also lets companies track exactly who accessed what or used which applications, when and from where, which can be important for auditing purposes as well as investigations, Imprivata says.

Goodbye privacy?
If all this sounds like a security guard's wet dream, there are critics who say it is likely to do more harm than good. As a tool for stopping crime, surveillance cameras are overrated, says security expert Bruce Schneier. "I think 9/11 has scared people, and they think that cameras will somehow magically save them. Cameras are cheaper than policemen, so it's perceived to be security on the cheap," he says. In fact, however, all they do is move crime around, Schneier says, citing research from Privacy International.

Face recognition might be useful for tracking members of the general public, but criminals can easily outwit it, Schneier says. "It'll be a whole bunch of years before the software (for automatic face recognition) gets that good, and even more before it recognises people who don't want to be recognised," he says.

In the meantime, a culture of universal surveillance is creating serious psychological side-effects, Schneier argues. The corporate interest in surveillance adds a new dimension to the problem, since the private sector has more of a free hand than government where it comes to collecting data.

"Companies can collect data that it is illegal for the government to collect, and then the government can use it," Schneier says. "Data has value. The rise in private sector surveillance mirrors the rise in data buying and selling. Companies will continue to eavesdrop on us because it is profitable to do so."