From the East German Stasi to modern-day cyber hackers, we take a furtive look at the people seeking to steal businesses' most valuable secrets, and what can be done to stop them.

From the East German Stasi to modern-day cyber hackers, Theo Leggett takes a furtive look at the people seeking to steal businesses' most valuable secrets, and what can be done to stop them.

Researcher Erik Meyersson explains how, at the height of the Cold War, the DDR - with the help of a network of thousands well-placed human assets - was able to produce cheap copies of one of IBM's most advanced computers.

Theo heads to Spymaster - a London high street retailer of James Bond-esque gadgets - to discover the modern tools of the trade, and to speak to Steve Durbin of the Information Security Forum, who explains how the greatest fear of big corporations that he works for is of being hacked.

The most prolific modern-day cyber-thief of corporate intellectual property is China, say some experts. Theo speaks to John Carlin, formerly an attorney general at the US Department of Justice, about his efforts to fend them off.

Producer: Laurence Knight

(Picture: Eye staring through a hole in a wooden fence; Credit: thornland/Getty Images)