lightsBranden Ghena pulls his car up under a traffic light in a city in Michigan. He plugs a radio transmitter into the car’s power adapter, connects it to his laptop and, with a few keyboard strokes, takes control of every traffic light in town. “We were able to advance the light,” Ghena says of the experiment, which took place in May. “We could make it turn green.” Ghena, an electrical engineer at the University of Michigan, and his team were exploiting a vulnerability in the light’s traffic controller. Present at every signalled intersection, the controller switches between red, yellow and green lights according to its programming. It can be set to change at regular intervals, or based on input from external traffic sensors. These controllers are often networked across a city, and receive commands via a sequence of data packets. This allows engineers to manage them remotely, but anyone with network access can send these commands. All Ghena had to do was figure out which sequences of packets corresponded to which controller commands, and he gained full control. More