A Researcher recently claimed that they were able to hack into a car computer system by embedding malware into a music CD. Possible ?
Researchers have been claiming for years that a cars computer can be hacked via blue tooth, wireless and local connections. Various articles have been posted over the past 2 years concerning this. Last year, a small group of researchers proved that they could control a car from a remote location after breaking into the vehicle. This was big news last year at Black Hat and DEFCON. At DEFCON alone, there was a new addition to the conference called "Car Hacking Village" where top researchers were demonstrating how easy it was. People attending could sit in on demonstrations or even sit down and play with what they learned.
But why disclose this information? Usually a disclosure is after manufacturers are working with Cyber Researchers and cover holes in their systems. Disclosure is usually is to inform and build a community of researchers around further discovers of other weaknesses and vulnerabilities.
So yes, this is very possible.
Can a vehicles computer be protected from external hacks? Absolutely.