If your car murmurs 'hello there,' your Bluetooth system has been hijacked

If you happen to hear a disembodied computer voice tell you to 'drive carefully' the next time you're behind the wheel, you've probably met the Car Whisperer.

Released late last week at the What the Hack computer security conference in Liempde, Netherlands, Car Whisperer is software that tricks the hands-free Bluetooth systems installed in some cars into connecting with a Linux computer.

Car Whisperer was developed by a group of European wireless security experts, called the Trifinite Group, as a way of illustrating the shortcomings of some Bluetooth systems, said Martin Herfurt, an independent security consultant based in Salzburg, Austria, and a founder of Trifinite.

The software takes advantage of the fact that many of these hands-free systems require only a very simple four-digit security key -- often a number such as 1234 or 0000 -- in order to grant a device access to the system. Many car manufacturers use the same code for all of their Bluetooth systems, making it easy for Car Whisperer to send and receive audio from the car.

Using a special directional antenna that allowed him to extend the normally short range of his Bluetooth connections to about a mile, Herfurt was able to listen and send audio to about 10 cars over a one-hour period recently.