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Replica of the Great Seal which contained aSoviet bugging device, on display at the NSA'sNational Cryptologic Museum.

The Thing (listening device)From Wikipedia, the free encyclopedia

The Thing, also known as the Great Seal bug, was one ofthe first covert listening devices (or "bugs") to use passivetechniques to transmit an audio signal. Because it waspassive, being energized and activated by electromagneticenergy from an outside source, it is considered apredecessor of RFID technology.[1]

Contents

1 Operating principles1.1 Technical details

2 Use3 United Nations4 See also5 Notes6 References7 External links

Operating principles

The Thing was designed by Léon Theremin,[2] who also made the theremin. It consisted of a tiny capacitivemembrane connected to a small quarter­wavelength antenna; it had no power supply or active electroniccomponents. The device, a passive cavity resonator, became active only when a radio signal of the correctfrequency was sent to the device from an external transmitter. Sound waves caused the membrane tovibrate, which varied the capacitance "seen" by the antenna, which in turn modulated the radio waves thatstruck and were re­transmitted by the Thing. A receiver demodulated the signal so that sound picked up bythe microphone could be heard, just as an ordinary radio receiver demodulates radio signals and outputssound.

Theremin's design made the listening device very difficult to detect, because it was very small, had nopower supply or active electronic components, and did not radiate any signal unless it was actively beingirradiated remotely. These same design features, along with the overall simplicity of the device, made itvery reliable and gave it a potentially unlimited operational life.

The principle of a resonant cavity microphone was patented by Winfield R. Koch of the Radio Corporationof America (RCA) in 1941. In US patent 2,238,117 he describes the principle of a sound­modulatedresonant cavity. High­frequency energy is inductively coupled to the cavity. The resonant frequency isvaried by the change in capacitance resulting from the displacement of the acoustic diaphragm.[3]

Technical details

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The device consisted of a 9­inch (22.86 cm) long monopole antenna (quarter­wave for 330Megahertz(MHz) frequencies, but able to also act as half­wave or full­wave, the accounts differ)—astraight rod, led through an insulating bushing into a cavity, where it was terminated with a round disc thatformed one plate of a capacitor. The cavity was a high­Q round silver­plated copper "can", with the internaldiameter of 0.775 in (19.7 mm) and about 11/16 in (17.5 mm) long, with inductance of about 10nanohenry.[4] Its front side was closed with a very thin (3 mil, or 75 micrometers) and fragile conductivemembrane. In the middle of the cavity was a mushroom­shaped flat­faced tuning post, with its topadjustable to make it possible to set the membrane­post distance; the membrane and the post formed avariable capacitor acting as a condenser microphone and providing amplitude modulation (AM), withparasitic frequency modulation (FM) for the re­radiated signal. The post had machined grooves and radiallines into its face, probably to provide channels for air flow to reduce pneumatic damping of the membrane.The antenna was capacitively coupled to the post via its disc­shaped end. The total weight of the unit,including the antenna, was 1.1 ounce (31 grams).

The length of the antenna and the dimensions of the cavity were engineered in order to make the re­broadcast signal a higher harmonic of the illuminating frequency. (Note that the transmitting frequency ishigher than the illuminating one.)[5]

The original device was located with the can under the beak of the eagle on the Great Seal presented to W.Averell Harriman (see below); accounts differ on whether holes were drilled into the beak to allow soundwaves to reach the membrane. Other sources say the wood behind the beak was undrilled but thin enough topass the sound, or that the hollowed space acted like a soundboard to concentrate the sound from the roomonto the microphone.

The illuminating frequency used by the Soviets is said to be 330 MHz.[6]

The Thing was discovered in a stroke of luck by a technician with an untuned video receiver—a widebandreceiver with a simple diode detector/demodulator, similar to some field strength meters. It was then locatedduring a technical surveillance counter­measures "sweep" of the Ambassador's office, using a signalgenerator and a receiver in a setup that generates audio feedback ("howl") if the sound from the room istransmitted on a given frequency; the generator was tuned to 1800 MHz. The device was first assumed tooperate on this frequency, but tests showed it was unstable and insensitive. Peter Wright, a British scientist,then got the Thing operating reliably at 800 MHz.

The membrane of the Thing was extremely thin, and was damaged during handling by the Americans;Wright had to replace it. Wright's examination led to development of a similar British system codenamedSATYR, used throughout the 1950s by the British, Americans, Canadians and Australians.

The simplicity of the device caused some initial confusion during its analysis; the antenna and resonatorhad several resonant frequencies in addition to its main one, and the modulation was partially bothamplitude modulated and frequency modulated. The team also lost some time on an assumption that thedistance between the membrane and the tuning post needed to be increased to increase resonance.

There were later models of the device, some with more complex internal structure (the center post under themembrane attached to a helix, probably to increase Q), and some American models with dipole antennas.Maximizing the Q­factor was one of the engineering priorities, as this allowed higher selectivity to theilluminating signal frequency, and therefore higher operating distance and also higher acoustic sensitivity.[7]

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Use

Theremin's device was used by the Soviet Union to spy on the United States. The device was embedded in acarved wooden plaque of the Great Seal of the United States. On August 4, 1945, a delegation from theYoung Pioneer organization of the Soviet Union presented the bugged carving to U.S. Ambassador W.Averell Harriman, as a "gesture of friendship" to the USSR's World War II ally. It hung in the ambassador'sMoscow residential study until it was exposed in 1952 during the tenure of Ambassador George F.Kennan.[8] The existence of the bug was accidentally discovered by a British radio operator who overheardAmerican conversations on an open radio channel as the Soviets were beaming radio waves at theambassador's office. The Department of State found the device in the Great Seal carving after an exhaustivesearch of the American Embassy, and Peter Wright, a British scientist and later MI5 counterintelligenceofficer, eventually discovered how it worked.[7][9]

United Nations

On the fourth day of meetings in the United Nations Security Council, convened by the Soviet Union overthe 1960 U­2 incident where a U.S. spy plane had entered their territory and been shot down, the U.S.ambassador showed off the bugging device in the Great Seal to illustrate that spying incidents between thetwo nations were mutual and to allege that Nikita Khrushchev had magnified this particular incident underdiscussion out of all proportion as a pretext to abort the 1960 Paris Summit.[10]

See also

Radio­frequency identification (RFID transmitters)Covert listening deviceNonlinear junction detectorTechnical surveillance counter­measures aka bug sweepingTEMPESTSurveillanceLéon ThereminPeter Wright

Notes1. Hacking Exposed Linux: Linux Security Secrets & Solutions (third ed.). McGraw­Hill Osborne Media. 2008.

p. 298. ISBN 978­0­07­226257­5.2. Glinsky, Albert, Theremin: Ether Music and Espionage, University of Illinois Press, Urbana, 20003. US Patent 2238117 (http://worldwide.espacenet.com/textdoc?DB=EPODOC&IDX=US2238117), Koch, Winfield

R, "Ultra high frequency modulator", published 1941­04­15, assigned to Radio Corporation of America(RCA).Retrieved 24 September 2013. "US 2238117 A (https://www.google.com.au/patents/US2238117?dq=US+2238117+A&hl=en&sa=X&ei=AjtBUuXUAs2ekgWKvICIBA&ved=0CEEQ6AEwAQ)" Google PatentSearch

4. Brown(?), Robert. M. (1967). "Electronic Eavesdroping" (http://books.google.cz/books?id=NkVJAQAAIAAJ&q=great+seal+bug+frequency+MHz&dq=great+seal+bug+frequency+MHz&hl=en&sa=X&ei=m2ALUefZBKjd4QTfiIGQBA&sqi=2&redir_esc=y). Electronics World (Ziff­Davis Publishing Company).Volume 77 (Issue3­6): p. 23. Retrieved 24 September 2013.

5. "Design How­To: Eavesdropping using microwaves – addendum" (http://eetimes.com/design/audio­

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design/4015284/Eavesdropping­using­microwaves­­addendum). EE Times (eetimes.com). United BusinessMedia. 12 November 2005. Retrieved 24 September 2013.

6. Pursglove, S. David (1966). "Great Seal Bug" (http://books.google.cz/books?id=E9gEAQAAIAAJ&q=great+seal+bug+frequency&dq=great+seal+bug+frequency&hl=en&sa=X&ei=QEsLUeiaDsnm4QSqiYHgCg&redir_esc=y). Electronic Design (Hayden Publishing Company). Volume 14 (Issues 14–17): p.35. Retrieved 24 September 2013.

7. Murray, Kevin. "THE GREAT SEAL BUG STORY" (http://www.spybusters.com/Great_Seal_Bug.html).Retrieved 2007­03­24.

8. George F. Kennan, Memoirs, 1950–1963, Volume II (Little, Brown & Co., 1972), pp. 155, 1569. Davis, Henry. "Eavesdropping using microwaves – addendum"

(http://www.audiodesignline.com/howto/173602214). Retrieved 2007­03­24.10. United Nations Security Council Verbatim Report 860. S/PV/860 (http://www.un.org/ga/search/view_doc.asp?

symbol=S/PV/860) page 15. 26 May 1960. Retrieved 2008­08­29.

References

Wright, Peter (1987). Spycatcher: The Candid Autobiography of a Senior Intelligence Officer. NewYork: Viking. ISBN 0­670­82055­5.Kennan, George (1967). Memoirs, 1925–1950. Little, Brown.Kennan, George (1983). Memoirs: 1950–1963. Pantheon. ISBN 978­0­394­71626­8.

External links

Passive Resonant Cavity & "Spycatcher" Technical Surveillance Devices(http://servv89pn0aj.sn.sourcedns.com/~gbpprorg/mil/cavity/index.html)The Great Seal Bug Story (http://www.spybusters.com/Great_Seal_Bug.html), Spybusters, Kevin D.MurrayA Trojan Seal (https://sm.asisonline.org/Pages/a­trojan­seal­006971.aspx) – Security Management,Ken Stanley, April 2010History of the Bureau of Diplomatic Security of the United States Department of State(http://www.state.gov/documents/organization/176589.pdf), October 2011, pp. 136–137

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Categories: Covert listening devices Espionage Espionage devices Espionage techniques KGBInventions by Léon Theremin Soviet Union–United States relationsSoviet Union intelligence operations Surveillance

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