Strategy Page on the most recent North Korean hoodwinking of western intelligence agencies:
Western intelligence agencies are a bit embarrassed that they were not able to predict the exact day that North Korea recently launched a long-range rocket. Even though North Korean announced the two week period during which the launch would take place last December, and several nations had photo satellites flying over the launch site regularly, the actual launch came as a surprise. The North Koreans apparently took advantage of the regular schedules of these spy satellites to move equipment around the launch site at the right time to conceal just how close the rocket was to takeoff. Many intel analysts had not seen this sort of thing at all (if they were young) and the older ones had not seen it done to this degree since the 1980s, when the Soviet Union was still around and using their maskirovka (“masking”) agency to carry out large scale deceptions of photo satellites. The Russians taught the North Koreans many things, and maskirovka was apparently part of the curriculum.
In addition to concealing weapons, their performance and movements, the Soviets also used satellite deception to mislead the west on how their troops would operate in the field. Several times a year, the Soviets would hold large scale maneuvers. Each of these exercises would involve many divisions, plus hundreds of aircraft and helicopters. Satellite photos of these maneuvers were thought to reveal tactics the Soviets were going to use in future wars. But the Soviets knew when American satellites were coming over and sometimes arranged displays of tactics they had no intention of using. Naturally, this made it more difficult for the Western intelligence analysts to figure out exactly what the Soviets were planning. This, of course, was the sort of confusion the Soviets wanted to create with these little deceptions.