https://www.apnews.com/51828908c6c8...-US-diplomats-in-Cuba-blamed-on-covert-device
In the fall of 2016, a series of U.S. diplomats began suffering unexplained losses of hearing, according to officials with knowledge of the investigation into the case. Several of the diplomats were recent arrivals at the embassy, which reopened in 2015 as part of former President Barack Obamas reestablishment of diplomatic relations with Cuba.
After months of investigation, U.S. officials concluded that the diplomats had been exposed to an advanced device that operated outside the range of audible sound and had been deployed either inside or outside their residences.
Cuba employs a state security apparatus that keeps many people under surveillance and U.S. diplomats are among the most closely monitored people on the island. Like virtually all foreign diplomats in Cuba, the victims of the incidents lived in housing owned and maintained by the Cuban government.
However, officials familiar with the probe said investigators were looking into the possibilities that the incidents were carried out by a third country such as Russia, possibly operating without the knowledge of Cubas formal chain of command.