A look at the world of espionage highlights some of the most famous spies in history, from Blinker Hall to modern-day cyber spies.

"The history of espionage is far older than any of today's intelligence agencies, yet the long history of intelligence operations has been largely forgotten. The codebreakers at Bletchley Park, the most successful World War II intelligence agency, were completely unaware that their predecessors in earlier moments of national crisis had broken the codes of Napoleon during the Napoleonic wars and those of Spain before the Spanish Armada. Those who do...