Automatic license plate reader cameras are controversial enough when law enforcement deploys them, given that they can create a panopticon of transit throughout a city.

At the Defcon hacker conference today, security researcher Truman Kain debuted what he calls the Surveillance Detection Scout.

The DIY computer fits into the middle console of a Tesla Model S or Model 3, plugs into its dashboard USB port, and turns the car's built-in cameras—the same dash and rearview cameras providing a 360-degree view used for Tesla's Autopilot and Sentry features—into a system that spots, tracks, and stores license plates and faces over time.

If a large group of Surveillance Detection Scout users were to combine their license plate recognition data—a feature that Kain has purposefully left out of the software—the system could create a crowdsourced version of the same powerful surveillance provided by commercial automatic license plate reader systems, whose use by police has been banned in some states.

"I’d be able to see everyone across the US, thousands of cars on this Surveillance Scout network," Kain says.

(Kain says it's far harder to link license plates to actual names, and he doesn't intend to include that data in his tool.)