This article is being published as part of a series related to the museum’s temporary exhibit From Spies to Satellites: The Cold War Era. The exhibit will be on display June 1 – Sept. 1, 2025.
During the Cold War, both U.S. and Soviet intelligence agencies raced against each other to develop new covert technologies to gather classified information. Read on to learn about two strange and fascinating listening devices, one from each side of the Iron Curtain.
The Great Seal Bug: A Soviet Spy Masterpiece
In August 1945, as the Allied victory in World War II was rapidly approaching, a group of Soviet students and members of the Young Pioneers presented U.S. Ambassador W. Averell Harriman with a handsome wooden carving of the Great Seal of the United States. This diplomatic gift hung prominently in the ambassador’s Moscow residence (Spaso House) for years. Little did the Americans suspect that the ornament concealed a technological marvel of espionage. Inside was a tiny passive listening device—ingeniously designed by Soviet inventor Léon Theremin, famed creator of the musical Theremin. The device, nicknamed “The Thing” by U.S. intelligence, had no power source or active circuitry. Instead, it remained dormant until Soviet operatives beamed a radio signal at it from outside. Upon illumination by the correct frequency, the hidden bug would resonate conversations in the room, causing a thin diaphragm to vibrate, modulating the return radio signal and broadcasting every word to the Soviet listening post. When the external signal stopped, the bug fell silent, making it nearly impossible to detect it with 1940s technology. For six years, Moscow’s security services quietly eavesdropped on U.S. diplomatic conversations through this “Great Seal Bug.”
The Great Seal bug’s discovery in 1952 came about almost by accident and clever sleuthing. Allied radio monitors in the early 1950s had accidentally picked up stray voices on secret frequencies—voices that turned out to be U.S. diplomats, hinting at a new Soviet eavesdropping method. In response, the State Department dispatched security specialists to sweep Spaso House. After several fruitless searches, technicians finally uncovered the hidden transmitter by baiting the eavesdroppers: as Ambassador George F. Kennan conspicuously “dictated” a classified note in his study, a technician roamed the house with a receiver until he caught the ambassador’s voice emanating from inside the Great Seal carving. The harmless-looking gift was pried open to reveal the tiny bug, exposing the Soviet operation.
The full strategic impact of the Great Seal bug became clear only years later. The U.S. kept the find secret until 1960, when Ambassador Henry Cabot Lodge Jr. dramatically unveiled the bug in front of the United Nations Security Council. This public disclosure came amid heated East–West tensions (just after the U-2 spy plane incident) and was intended to embarrass the Soviets by revealing their infiltrations. Lodge even asserted that over 100 similar Soviet bugs had been discovered in U.S. missions across Eastern Europe. The Great Seal bug thus became emblematic of early Cold War espionage, demonstrating the USSR’s willingness to push technological boundaries to spy on its rival. Soviet bugging of U.S. installations would continue throughout the Cold War, with the notable example of the mass surveillance campaign of the U.S. embassy in Moscow throughout its construction in the 1980s. Today, a replica of the bugged seal—its interior components visible—is displayed in the NSA’s museum as a testament to this unusual espionage coup.
Project “Acoustic Kitty”: America’s Spy Cat Experiment
Across the Iron Curtain, the United States explored its own extraordinary espionage ideas. In the 1960s, the CIA’s Directorate of Science & Technology embarked on Project “Acoustic Kitty,” a top-secret effort to turn an ordinary street cat into a roaming eavesdropping device. The motivation was straightforward: cats moved freely in public and around foreign embassies without arousing suspicion. If a cat could carry a microphone and transmitter, it might slip close to unwitting targets (say, a Soviet official on a park bench) and covertly transmit their conversation. In an era where the intelligence arms race was at its peak, a way for the U.S. to safely gather information on Soviet diplomatic and military movements was heavily pursued. Yet, this plan required surmounting major technical and training challenges. According to declassified accounts, Agency technicians surgically implanted a microphone in the cat’s ear canal, worked with outside audio contractors to build a ¾-inch-long transmitter to embed near the base of the skull, and ran a fine wire antenna along the animal’s tail under the fur. The surgery packed batteries and electronics into the feline without visibly altering its appearance or behavior. After years of trials (reportedly 1961–1966), the first “Acoustic Kitty” was deemed ready for a field test.
While the technical feasibility of the operation was a success, the field implementation of the acoustic kitty was far less so. In the unofficial version of the story, CIA handlers released their bugged cat near a Soviet compound in Washington, D.C., aiming it toward two men on a park bench. The cat, however, had other ideas. Distracted or following its own feline instincts, it wandered into the street—where it was promptly run over by a taxi, to the horror of the agents monitoring from a van. The multi-million-dollar experiment ended during its first trial. By 1967 the project was scrapped, with CIA officials dryly concluding that while cats could be trained to move short distances, using them as clandestine eavesdroppers “would not be practical.” One internal report hailed the attempt as a “remarkable scientific achievement” despite its failure—praising the technicians as pioneering scientists for even managing to guide a cat’s behavior to any extent. In the end, however, biology and unpredictability prevailed over technology: a cat simply could not be reliably controlled in the open, especially given hunger and curiosity that no wiring could fully suppress.
Modern disclosures debate the genuineness of these old accounts. Some CIA insiders later claimed that the dramatic taxi incident was a myth—a tongue-in-cheek remark by a former officer that took on a life of its own. According to a CIA historical review, the cat was in fact treated humanely, and the equipment was removed without harm when the project ended. The official line is that the feline agent survived and simply proved too independent to follow “orders.” In other words, “the cat wanted to do what the cat wanted to do,” according to a CIA official. Regardless of which ending one prefers, Operation Acoustic Kitty stands as a bizarre episode of Cold War espionage. It exemplified the era’s experimental zeal: American espionage experts were willing to invest vast time and money (by one account $15–20 million) in an outlandish scheme if it offered even a faint edge over the Soviets.
Cold War Ingenuity and Rivalry
Though one operation was Soviet and the other American, the Great Seal Bug and Acoustic Kitty share a common legacy. Both illustrate the extraordinary, sometimes absurd lengths to which the rival superpowers went to win their spy-vs-spy contest. In an age when the Cold War often played out in the shadows, each side combined cutting-edge science with creativity—from embedding a bug in a diplomatic gift to implanting a transmitter in a living animal—to outwit the other. These two efforts, one highly successful and one a notorious failure, remind us that the intelligence struggle was not only about missiles and armies but also about ingenuity and daring. In pushing the boundaries of technology and tradecraft, the United States and the Soviet Union revealed that no idea was too strange if it might confer an advantage.
Sources
- National Security Agency:
- International Spy Museum:
- “The Thing” museum exhibit: https://www.spymuseum.org/exhibition-experiences/about-the-collection/collection-highlights/the-great-seal/
- Crypto Museum:
- Inner workings of “The Thing”: https://www.cryptomuseum.com/covert/bugs/thing/
- Central Intelligence Agency:
- Animals in Espionage: https://www.cia.gov/stories/story/natural-spies-animals-in-espionage/#:~:text=The%20technology%20worked%2C%20but%20the,we%20wanted%20it%20to%20go
- George Washington University archive of CIA document outlining “Views on Trained Cats Use” (March 1967): https://nsarchive2.gwu.edu/NSAEBB/NSAEBB54/st27.pdf
- Smithsonian Magazine:
- Sensorystudies.org:
- CIA sensory experimentation and connection to cats: https://www.sensorystudies.org/picture-gallery/deprivation-2/
Above links were live at the time this post was published.
