Over the last 15 years or so, automakers have begun installing what most people refer to as a "black box" device in some cars. Initially, these black boxes, or Event Data Recorders as they are more formally known, were designed to collect data such as speed, braking, and throttle information in the event of a crash to help automakers improve the safety of their vehicles.
The black boxes found in cars are not nearly as intrusive as those found in airplanes which record cockpit conversations and a host of other bits of information which can all be played back. The black box in your car can't record sounds or video, so most of your secrets are safe. On the other hand, if you were speeding, failed to brake, or stepped on the accelerator just prior to a crash, that data is safely locked inside the black box.
Ford, GM and Chrysler have licensed their data encryption schemes so that insurance companies can access the data when investigating accidents, says a report by ABC News. Honda, Toyota and BMW, on the other hand have not, as yet, licensed their codes so black boxes in these vehicles can only be decoded by sending the black box back to the factory for analysis.
States have different rules about who can access the information in your black box, and under what circumstances. In some states a warrant or the owner's consent is required for law enforcement or the insurance company to access the data.
The National Highway Traffic Safety Administration, says Wired Magazine, is considering whether to require black boxes in all vehicles and standardizing what data they collect as early as this year. Given the fact that the NHTSA estimates that about 85% of all cars sold in the United States in 2010 already had black boxes, the only change a national standard might create is giving customers a better idea of just what information is being collected.
So the answer is no, your car isn't spying on you, but it does store some data that could be used to determine fault in an accident.