Remember that old Rockwell song “I always feel like somebody’s watching me”? Well, it wasn’t just his imagination. We are all being watched constantly. Whether you’re on the street, the subway, or even in your home, electronic eyes are searching for criminals and terrorists with technology that can make the invisible visible. Step behind the security doors and discover the secret–often disturbing–world of surveillance.

Surveillance has been defined as the close observation of a person, particularly one under suspicion. This is most commonly done with CCTV. But this technology has two limitations: First, you have to know who you’re looking for. And second, you have to have a human watching every screen every minute of every day.

London, for instance is the most heavily surveyed city in the world with over half a million cameras. The average Londoner is filmed by over 300 cameras during the course of the day. Although that was unable to stop the suicide bombers in 2005, the information gathered from the hours of recording was very useful in the investigation.

Then there’s Las Vegas where every year 35 million visitors flock to casinos. Powerful cameras 40 feet away can read the serial number on a dollar bill or the dial on a wrist watch.

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