We get into an Uber car, and the driver passes by the Kremlin walls, guided by GPS. At the end of the ride, the bill turns out to be three times as expensive than usual. What is the matter? We check the route, and the screen shows that we travelled to an airport outside of Moscow. Impossible. We look again: the moment we approached the Kremlin, our location automatically jumped to Vnukovo. As we learned later, this was caused by a GPS fence set up to confuse and disorient aerial sensors, preventing unwanted drone flyovers.