The Thing, also known as The Great Seal Bug, was a passive covert listening device, developed in the Soviet Union and planted in the study of the US Ambassador in Moscow, hidden inside a wooden carving of the Great Seal of the United States. It is called a passive device as it does not have its own power source. Instead it is acivated by a strong electromagnetic signal from outside. The device was code named LOSS by the US and RAINDEER by the Soviets.
On 4 August 1945, the Vladimir Lenin All-Union Pioneer organization 1 presented a hand-carved replica of the Great Seal of the United States to US Ambassador Averell Harriman, as a gesture of friendship to the USSR’s World War II ally. It hung in the library at the Residency Spaso House.
Unknown to the Americans however, the carving contained an HF radio bug of a novel design, in that it didn’t have its own power source and was not connected via wires. Instead, the device was illuminated by a strong radio signal from the outside, which powered and activated it. It gave the bug a virtually unlimited life and provided the Soviets with the best possible intelligence.
The bug was finally discovered by the US State Department in 1952, three ambassadors later, during the tenure of Amb. George F. Kennan.
In 1951, a British radio operator was monitoring Russian air force radio traffic, when he suddenly picked up the voice of the British Air Attaché loud and clear, but a survey of the embassy did not reveal any hidden microphones. A similar thing happened to an American interceptor in 1952, when he overheared a conversation that appeared to come from the ambassador’s residency at Spaso House. After a search by the Department of State, the bug was finally discovered by means of a so-called crystal-video receiver , whilst the Russians were actively illuminating the bug.
The device appeared to be hidden inside the wooden carving behind the ambassador’s desk, and resembled a cylindrical microphone with an antenne rod connected to it. Tiny holes in the wood under the eagle’s beak, guided the sound to the membrane of the bug that was mounted just behind it. When the Russians knew that an important meeting would take place, they parked an unmarked van in the vicinity of the residency 3 and illuminated the bug. A receiver, tuned to the bug’s resonant frequency, was then used to pick up the conversation in the ambassador’s office.
The discovery of the bug was kept secret for many years, until the 1960 U-2 incident . On 1 may 1960, the Soviets had shot down an American U-2 spy plane over Soviet airspace, as a result of which the Soviet Union convened a meeting of the United Nations Security Council, accusing the Americans of spying. On the 4th day of the meeting (26 May 1960), in an attempt to illustrate to the council that spying between the two nations was mutual, American Ambassador to the UN, Henry Cabot Lodge, revealed the Russian bugging device.
The Thing consisted of a tiny capacitive membrane connected to a small quarter-wavelength antenna; it had no power supply or active electronic components. The device, a passive cavity resonator, became active only when a radio signal of the correct frequency was sent to the device from an external transmitter. This is currently referred in NSA parlance as “illuminating” a passive device. Sound waves (from voices inside the ambassador’s office) passed through the thin wood case, striking the membrane and causing it to vibrate. The movement of the membrane varied the capacitance “seen” by the antenna, which in turn modulated the radio waves that struck and were re-transmitted by the Thing. A receiver demodulated the signal so that sound picked up by the microphone could be heard, just as an ordinary radio receiver demodulates radio signals and outputs sound.
Theremin’s design made the listening device very difficult to detect, because it was very small, had no power supply or active electronic components, and did not radiate any signal unless it was actively being irradiated remotely. These same design features, along with the overall simplicity of the device, made it very reliable and gave it a potentially unlimited operational life.