U.S. Navy operation to plant an intercept device on a Soviet underwater communications cable at a depth of some 400 feet in the Sea of Okhotsk. Submarines, possibly using a minisub, periodically serviced the device and recovered tapes from it.

The cable, between Soviet bases on the Kamchatka Pennisula and the Soviet Far Eastern coast, carried highly classified military, as well as civilian, communications. The bug was placed on the cable by the U.S. nuclear-propelled submarine Halibut, which also replaced the tapes from the start of the operation until 1976, when the nuclear-propelled submarine Parche took on the job. Both submarines had been extensively modified for seafloor work and recovery operations.

Although the communications on the tapes were weeks or months old, they were still valuable to intelligence analysts. Some of the communications pertained to future events that could be monitored when they took place. The data also provided technical intelligence.

Ivy Bells continued until 1981 when U.S. satellite photos showed Soviet salvage ships working over the exact spot where the intercept pod had been attached to the seafloor cable. Subsequently, when the Parche went in to replace the tapes, the pod was missing. The Navy and other intelligence agencies were unable at the time to determine how or exactly when Ivy Bells was compromised.

With the arrest of NSA analyst Ronald Pelton, the Navy learned that he had revealed the top secret Navy operation to the Soviets about Jan. 1980. (One of the seized seafloor recording devices is now on display in the museum at the former KGB headquarters in Moscow.)