Paula Cambronero was studying public relations at a Costa Rican college when she landed her first real job working for a U.S. government contractor. But it wasn’t to write press releases.

As part of a program shrouded in secrecy to build a “Cuban Twitter” on the Communist-governed island, Cambronero profiled Cuban cellphone users, categorizing them as “pro-revolution,” ”apolitical” or “anti-revolutionary.”