Much ado has been made over flying drones in groups, but there hasn't been much thought given to protecting autonomous drone groups against security breaches. What happens if someone impersonates enough drones to hijack their collective decision-making process? MIT might have a viable defense. Its researchers have developed a positioning technique that would prevent and mitigate these kind of impostor attacks. The key is to give each drone a wireless fingerprint that reflects its interaction with the environment -- effectively, the network can tell the difference between the actual drone pack and a fraud operating from the outside.