Richard, a professional hacker, was hired by a marketer to gather sensitive data and information...

Richard, a professional hacker, was hired by a marketer to gather sensitive data and information about the offline activities of users from location data. Richard employed a technique to determine the proximity of a user's mobile device to an exact location using CPS features. Using this technique. Richard placed a virtual barrier positioned at a static location to interact with mobile users crossing the barrier, identify the technique employed by Richard in this scenario.