Disclosed herein is a method and system for determining plausibility of intelligent transport system (ITS) messages via a wireless communications channel at one or more message receivers. The method includes receiving a first ITS message having a first characteristic and receiving a second associated ITS message having a second characteristic. The method uses the first characteristic and the second characteristic to satisfy at least one predetermined criterion and determines plausibility of at least one of the first ITS message, the second ITS message and a third ITS message. The characteristic includes a PHY-layer or MAC-layer characteristic. The method is used to distinguish between genuine and spoofed messages to reduce the possibility of an attack.