Even if you’re not a Cuban spy, you too can receive secret messages sent by Havana to its spooks in Miami, Washington and around the world.
Every week, one short wave radio station in Cuba
broadcasts 97 messages coded in fax-like tones. A computer program
easily available to the public changes the tones into numbers, and the
Cuban spies then decode the numbers into words.
A second Cuban spy
station transmits 16 messages per week in the dots and dashes of the
175-year-old Morse code – secret messages to Havana spies who may be
older or less technologically savvy.
Sixteen years after the arrests in Miami of five Cuban spies who
got their secret orders by short wave transmissions, Havana is still
using a system that fell out of favor in the cloak-and-dagger world with
the end of the Cold War.
Source : http://www.miamiherald.com/2014/02/16/3939953_cuban-spies-received-secret-messages.html