The Federation Reconnaissance Office or FRO was the civilian espionage and intelligence agency of the United Federation of Planets. The FRO focuses on signals intelligence, responsible for remotely monitoring every observable segment of the galaxy, and intercepting foreign communications. (TNG novel: Collateral Damage)
Unlike its counterparts in Starfleet Intelligence, and to a certain extent, the Federation Security Agency, the Federation Reconnaissance Office does not employ field operatives for intelligence collection purposes. Rather, the Office relies on specialists who maintain the technological systems they use to collect sensitive information.
The Federation Reconnaissance Office was part of the Federation Intelligence Community, and high-ranking officials from the FRO participated in the Federation Security Advisor's daily intelligence services briefings held at the Palais de la Concorde to coordinate the various agencies' efforts. In January 2387, the intelligence official who represented the FRO at these briefings was J. Chapman Shull of United Earth. (TNG novel: Collateral Damage)
Based on the duties and responsibilities of the organization, the Federation Reconnaissance Office is comparable to real-life organizations such as the United Kingdom Government Communications Headquarters (GCHQ) and the United States National Security Agency (NSA). Both of which are tasked with the global monitoring, collection, and processing of information and data for foreign and domestic signals intelligence (SIGINT).