The masterminds discovered a way to hack into OnStar, the General Motors telematics system. After figuring out how to hook into OnStar's emergency communication system, they overwhelmed it with data. While the computer was busy trying to manage the overrun of data, the research team inserted code that took control of the sedan's other computers, giving it control. So while reporter Leslie Stahl tooled around in a parking lot, a DARPA researcher with a laptop would occasionally take control of the car, like by applying its brakes or, conversely, removing the ability for Stahl to use the brakes.
Hacking into vehicles has been in the news for years: Car and Driver ran a feature on the various ways cars could be hacked in 2011, two hackers released a car-hacking code at the hacker-fest Defcon in 2013 and demonstrated how it worked on a Toyota Prius and Ford Escape, and German researchers demonstrated how they could hack into BMW's Connected Drive remote-services system last week via an attack on the cars' telematics units. This isn't about GM or Onstar or the future; hacking into cars of all kinds isn't coming, it's here, and it doesn't take the half-billion-dollar annual budget of a small DARPA division to do it.
Check out the 60 Minutes video on the CBS site (you can watch the entire video from a mobile device without logging in). The OnStar hacking starts at 6:45, but it's worth watching what leads up to that.