Now imagine a backdoor planted not in an application, or deep in an operating system, but even deeper, in the hardware of the processor that runs a computer. And now imagine that silicon backdoor is invisible not only to the computer's software, but even to the chip's designer, who has no idea that it was added by the chip's manufacturer, likely in some farflung Chinese factory. And that it's a single component hidden among hundreds of millions or billions. And that each one of those components is less than a thousandth of the width of a human hair.

In fact, researchers at the University of Michigan haven't just imagined that computer security nightmare; they've built and proved it works. In a study that won the "best paper" award at last week's IEEE Symposium on Privacy and Security, they detailed the creation of an insidious, microscopic hardware backdoor proof-of-concept. And they showed that by running a series of seemingly innocuous commands on their minutely sabotaged processor, a hacker could reliably trigger a feature of the chip that gives them full access to the operating system. Most disturbingly, they write, that microscopic hardware backdoor wouldn't be caught by practically any modern method of hardware security analysis, and could be planted by a single employee of a chip factory.