April 2019: A yearlong study by security experts with the Washington-based think tank C4ADS conducted by identified a pattern in which GPS devices near Putin and his entourage suddenly gave incorrect readings. The researchers also identified five buildings associated with the Kremlin that appeared to employ the technique on a rolling basis. The researchers theorize that one reason "spoofing" is deployed is to protect Putin and other Russian officials from attacks or surveillance by drones that rely on GPS.

However, there's a drawback to creating a GPS bubble around a world leader, said Todd Humphreys, an engineering professor at the University of Texas at Austin, who was involved with the study. It also makes it easier to keep track of Putin. "What's ironic is if you look at these patterns, and if you coordinate it with the movements of the leader of Russia, it appears you have a Putin detector," Humphreys said. In other words, if you detect spoofing, there's a good chance Putin may be nearby.

Read the full articles featuring Dr. Humphreys on CBS News and Foreign Policy. In addition, check out this segment from the Daily Show with Trevor Noah and an interactive version of the report, "Above Us Only Stars."