The overwhelming nexus of communication in 2199 is the Matrix, an unthinkably complex conglomeration of digital communications of sound, imagery, neural impulses, and data.
More secure, but more limited, are the direct physical networks used within arcologies, land-based data lines to convey the same information but inaccessible to the Matrix.
Making a phone call, with or without visuals, one runs the information over the Matrix. Simstim programs are received via the Matrix. And of course, internet data exchanges are conducted with the Matrix. The security of communication varies with the wealth and skill of every sender and receiver and their systems.
Most communications are nominally encoded to prevent casual interception, but some use sophisticated programs to track the communications, detect attempts at interference, and counter such interference with ICE (Intrusion Countermeasures Electronics, typically designed to send electromagnetic impulses to overload and damage offending computer systems and any netrunner who is controlling them with a direct neural interface).
