When I read articles about the potential security issue with GPS, my fist reaction was “How can they hack a GPS without interfering with the satellite signals?“. In fact, it’s much more simple! More and more GPS models on the market come with a builtin TMC receiver (Traffic Message Channel) which works over the RDS. That’s it!
They were able to sent fake TMC messages to GPS receivers (up to 16 Kms!). Those messages can contains funny information such as a road blocked by a space shuttle or kangaroos or worse an airplane crash. It can quickly freeze the traffic and cause big incidents.
Another application could be commercial TMC messages: Be sending fake into, the GPS will suggest the driver to pass in front of a commercial center…
Conclusion: once a device has a door open to the world to receive external data, there are security risks! Never trust unsigned or unchecked material.