The New York Review of Books

“Brute force” is a phrase which turns up often in James Bamford’s useful investigation of the National Security Agency, the largest but least known of American intelligence services. As used by NSA officials, “brute force” refers to the method of last resort in cracking secret codes. The best method is to obtain the key to the code by stealing it, buying it, or figuring it out, but that is often impossible. A “brute force” attack simply tries out all the possible keys to a code identified through intercepted messages.

These possibilities can be very numerous. A commercial cipher with a fifty-six-bit key devised by IBM in the mid-1970s, for example, would present an inquisitive outsider with about seventy quadrillion possibilities. Large as that number is, a computer could be built with speed and capacity enough to try out every last one of them in less than a day. This helps to explain why the NSA’s headquarters at Fort Meade, Maryland, is the computer capital of the world. Lt. Gen. Marshall S. Carter, director of the NSA (DIRNSA) for just over four years between 1965 and 1969, told Bamford he was in charge of five and a half acres of computers. Another NSA official told him that computer acreage is now about double what it was in Carter’s day.

It is the scale of the NSA that impresses. According to Bamford, the NSA’s main building at Fort Meade contains about 1.9 million square feet of floor space, roughly equal to the CIA’s headquarters in Langley, Virginia, and the Capitol building in Washington combined. It has employed as many as 95,000 people, classifies 50 million to 100 million documents a year, produces 40 tons of classified waste per day, has up to $1 billion in contracts out at any given time, and has an annual budget of perhaps $10 billion.

Making, breaking, and protecting codes is only part of the work conducted by this vast establishment, and the smaller part at that. The larger part is collecting and analysing COMINT, SIGINT, and ELINT. COMINT and SIGINT are communications and signals intelligence—messages of every conceivable type, from ordinary commercial cables to Soviet naval communications to ships at sea. When the Soviet space capsule Soyuz I ran into trouble during reentry in April 1967, technicians at an NSA listening station in Turkey taped the whole awful event, from the first discussion of problems with the parachute through the cosmonaut’s final farewell to his wife and a terminal scream when the capsule burned up as it plunged into the earth’s atmosphere. Also included under the general heading of SIGINT are radio transmissions of a technical nature such as radar or telemetry broadcast by Soviet missiles during test flights, the principal source of American intelligence about the performance of Soviet strategic weapons. ELINT is electronics intelligence, defined as electromagnetic radiators with a non-atomic origin. (HUMINT—human intelligence collected by traditional espionage—is the province of the …