The U.S. State Department recently revealed that some government employees working in the U.S. embassy in Havana, Cuba were sent home due to symptoms resembling a concussion, with at least one employee suffering from hearing loss. State Department officials have said this was an “acoustic attack,” using sonic devices outside the range of audible sound that were placed either inside or outside the diplomats’ residences. This week, The Cipher Brief’s Kaitlin Lavinder spends 15 minutes with H. Keith Melton, an intelligence historian, author, and board member of the International Spy Museum, who recently co-authored Spy Sites of Washington, DC with former CIA Director of the Office of Technical Service Robert Wallace. Here, they talk about the history of espionage activities between the U.S. and Cuba, and which country is the biggest espionage threat to the United States.