Passing and Analyzing Information

Photo courtesy U.S. Department of Justice A letter hidden Aldrich Ames left at a dead drop for his KGB contact.

­When secret information is passed to the spy's controllers, it must be hidden so that the enemy doesn't suspect anything. This could ruin the spy's cover, or lead the enemy to deliberately supply misinformation. Until the early 20th century, spies resorted to invisible inks to hide messages between the lines or on the bac­k of non-suspicious correspondence. Sugar solutions or lemon juice are invisible until heated. Other chemicals don't appear until the paper is painted with a specific reagent.

One time-tested method for relaying information is the dead drop. A dead drop is a secret hiding place somewhere in public. It could be behind a loose brick in a wall at the city park, or in a plant at a certain street corner. When a spy has a message to send, he goes about his business, perhaps picking up some dry cleaning or seeing a movie. He passes by the dead drop and deposits the message casually, without arousing suspicion. The spy then has to leave a signal to let his handlers know there is a message to be retrieved. A chalk mark on a lamppost, a certain color of sheet on a clothes lines or even a cryptic message in the classified section of a newspaper are all possible signals. A spy may use several dead drops so he isn't noticed repeatedly visiting the same loose brick.

­Spy controllers can use one-way communication t­o issue instructions to spies. The mysterious numbers stations in operation around the world are almost certainly used for this purpose. A numbers station is a government operated radio station broadcasting intermittently on the short-band frequencies. A certain song or announcement will mark the beginning and end of each broadcast, which consists solely of a voice, possibly altered electronically, reciting a long series of numbers. The numbers are coded messages deciphered by the intended recipient using a virtually unbreakable cipher known as a one-time pad.

A great deal of espionage revolves around secret codes. Information transmitted between spies and controllers is usually coded, and a large proportion of government and military communications are encoded, particularly during wars. Many spy missions have the sole purpose of acquiring the keys needed to solve these codes, or obtaining the devices used to encode and decode messages.

Data Analysis
The acquisition and transmission of secret information is meaningless if the information isn't properly analyzed and acted upon. Russian leader Joseph Stalin was provided with information from several agents that Germany was going to break the German-Russian alliance and attack Russia during World War II, but he refused to believe it. Russian forces were not properly aligned or prepared when the German attack came.

Data analysts take information from numerous sources, not just spies, and develop an overall picture of enemy strategies and policies. This information is then written into briefings for political leaders. While information from a single source may be untrustworthy, additional sources can be used to corroborate the data. For example, U.S. code breakers had partially cracked the Japanese Purple code during World War II, and they were fairly certain that Japan was planning an attack at Midway Island. They weren't completely sure if they were reading Japan's code word for the island (AF) correctly, however, so they had troops positioned at Midway to issue a radio alert saying they were running short on fresh water. Shortly, Japanese communications were intercepted that reported that AF was low on fresh water, confirming the target of the coming attack.

Secret Codes During WWII Photo courtesy National Security Agency An Enigma machine During World War II, the German military used a device known as an Enigma machine to send coded messages. The machine functioned somewhat like a typewriter with a maze of complicated mechanical and electronic connections. Any message typed into the machine would be transposed into a code; another Enigma with the identical set-up of wires and rotors could reverse the code and reveal the original message. Polish code breakers had cracked the Enigma code and built duplicate Enigma machines before World War II. They shared their knowledge with the British, who used it, along with several captured Enigmas, to decipher an enormous volume of coded Nazi messages, some from Hitler himself. This information, codenamed ULTRA, was kept under tight wraps so that the Germans would not suspect that their messages were being read.