(Bloomberg) – Internet-connected and driverless cars could be targets for hackers — potentially including terrorists and hostile nations — so the automotive industry must ensure vehicles have built-in cyber security protection, a top U.S. Justice Department official said.

"There is no Internet-connected system where you can build a wall that's high enough or deep enough to keep a dedicated nation-state adversary or a sophisticated criminal group out of the system," John Carlin, U.S. assistant attorney general for national security, said Tuesday at an auto industry conference in Detroit.

Plugging security gaps

The burgeoning market for cars connected to the Internet is expected to be valued at about $42 billion by 2025, with more than 220 million vehicles on the roads. Companies are expanding investments in telematics, which combines computers and wireless technology to provide services such as infotainment and real-time traffic updates to moving vehicles. Toyota Motor Corp., Google,  Ford Motor Co., and Baidu Inc. intend to introduce driverless cars in as soon as five years.