In news that should surprise very few, connected cars remain a complete privacy nightmare. But now we have a better idea of what data those cars are giving away, and to whom, thanks to a study conducted by a team of researchers at Northeastern University and Consumer Reports. Testing 21 cars from 19 different brands revealed patterns of traffic to advertisers and trackers, as well as data shared with Big Tech firms like Microsoft and Adobe. And using a car’s companion app can multiply the problem, their testing found.

In 2023, the Mozilla Foundation published a widely covered report looking at the privacy policies of more than two dozen automakers. They were appalled, writing that “cars are the worst product category we have ever reviewed for privacy.”But that analysis was conducted by sitting down and reading all the various privacy policies of each brand; today’s study involved measuring traffic from actual cars under a number of scenarios, including idling and being driven. The researchers even parked 11 cars—just the electric ones—in a Faraday tent to see if the loss of a cellular signal would push that traffic to the car’s Wi-Fi connection instead.

Attempts to actually see what was in the data packets using modified certificates failed in every case. But “the network traces still yielded valuable information, including the domains contacted via DNS traffic, Server Name Indication (SNI) in TLS handshakes, the volume and timing of transmissions, and differences in behavior across experimental scenarios,” they found.