The researchers, mostly chaps called Wang, published their findings in a lengthy paper with the title Defending against Sybil Devices in Crowdsourced Mapping Services (PDF).
"Our experiments show that a single Sybil device with limited resources can cause havoc on Waze, reporting false congestion and accidents and automatically rerouting user traffic," they wrote.
"More importantly, we describe techniques to generate Sybil devices at scale, creating armies of virtual vehicles capable of remotely tracking precise movements for large user populations while avoiding detection."