You're talking about a GPS repeater. Such systems are commercially available to rebroadcast a GPS signal within a building where the signal wouldn't penetrate, but require a license to operate, IIRC.

As for countermeasures, well, whoever's holding the receiver is bound to get suspicious if they move and the reported position doesn't. :) Jokes aside, there is work being done integrating other sensors (inertial, compass, gyro, etc.) to do dead reckoning to detect errors in the position and motion reported by the GNSS receiver.

As an aside, "GPS" technically refers only to the positioning system operated by the United States. The generic term is "GNSS" (global navigation satellite system) and encompasses GPS, GLONASS, Galileo, Beidou, etc.)