SignalTrace flips the script on license plate readers: a camera that used to just record plates now scoops up the Bluetooth and WiFi identifiers from every phone, wearable, and Bluetooth-enabled device inside passing cars. Leonardo, the surveillance company behind this, isn't shy about the goal. They want law enforcement to track specific people, not just vehicles.
How ALPRs Get a Second Snout
Automatic license plate readers are already everywhere across the U.S.—mounted on police cars, bridges, toll booths, and private parking lots. They snap plate numbers and log time, location, and often an image. SignalTrace bolts on additional sensors that listen for Bluetooth and WiFi probe requests. Your phone broadcasts a unique MAC address every few seconds looking for known networks. Wearables do the same. SignalTrace captures those, links them to the plate, and suddenly a vehicle-centric system becomes a people-tracking grid.
Why This Matters More Than the Usual Surveillance FUD
I've watched ALPRs creep into quiet suburbs under the guise of stolen-vehicle recovery. Adding passive wireless sniffing is a logical, nasty next step. The same hardware can now map who was in a car—driver and passengers—even if they parked and walked away. Law enforcement doesn't need a warrant for these identifiers because courts have treated Bluetooth and WiFi probe signals as voluntarily broadcast. SignalTrace exploits that legal gray zone without firing a shot.
Schneier's point about smartphone data is worth zoning in on: SignalTrace is bad, but it's a rounding error compared to the data Apple, Google, and carriers already vacuum up. A single ALPR with SignalTrace might log a few hundred devices per hour. Your phone chain-saws through location, app usage, contacts, and browsing history 24/7. SignalTrace doesn't break new ground—it just puts a familiar tracking power into a new set of hands, often local police who lack the technical chops to ask for the phone-company data the easy way.
Leonardo hasn't published deployment numbers or costs, but the tech is ready now. SignalTrace turns every ALPR in the fleet into a passive Stingray for short-range identifiers. Expect to see these retrofit kits sold aggressively to police departments that already bought into ALPR infrastructure. The next time you drive past a camera, remember: it's probably not just reading your plates anymore.
Source: Enhanced License Plate Tracking
Domain: schneier.com
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