Over the past few years, owners of cars with keyless start systems have learned to worry about so-called relay attacks, in which hackers exploit radio-enabled keys to steal vehicles without leaving a trace. Now it turns out that many millions of other cars that use chip-enabled mechanical keys are also vulnerable to high-tech theft.

Get in-depth coverage of current and future trends in technology, and how they are shaping business, entertainment, communications, science, politics, and society.