It wasn’t too surprising when scientists first hacked into a car using its own onboard diagnostic port—sure, it’s easy to get into a car’s electronic brain if you’re already inside the car. Now the science of car-hacking has received a digital upgrade: Researchers have have gained access to modern, electronics-riddled cars from the outside. And in so doing, they’ve managed to take control of a car’s door locks, dashboard displays, and even its brakes.

The oddest part of these findings, which were presented this week to the National Academy of Science’s Committee on Electronic Vehicle Controls and Unintended Acceleration, is that they weren’t entirely intentional: It was all part of an investigation prompted by the Toyota acceleration problems, and was meant to probe the safety of electronic automotive systems. But testing those system’s safety also uncovered some flaws.

How It Works

The researchers took a 2009 sedan (they declined to identify the make and embarrass the manufacturer) and methodically tried to hack into it using every trick they could think of. They discovered a couple good ones.

By adding extra code to a digital music file, they were able to turn a ...