Motion Sensor Key Fobs and Relay Theft: What They Do (and Don’t) Protect Against

Some key fobs include a motion sensor that switches the key fob into “sleep mode” if it’s been motionless for a few minutes. This stops the key fob from transmitting and a sleeping key fob won’t respond to relay equipment, so relay car theft is usually prevented — provided the key fob’s motion sensor and firmware are well-designed. Motion sensor key fobs only help if the key fob is left completely still. They offer no protection when the key fob is carried around in a pocket, or when thieves target car owners standing in queues at a takeaway for example. Some less well engineered key fobs have motion sensors with a long time out period before they “sleep”.

Some car manufacturers will replace vulnerable key fobs supplied without motion sensors, with new motion sensor ones—but usually at a cost.

Unfortunately, only a minority of key fobs use motion sensors.

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