Not sure how practical their example is, but I'd always heard this was simply impossible to do, and even a week or two ago, when people said the NSA or FBI could do it, lots of tech experts said that was crazy talk. Well, maybe not, according to the Washington Post:

While controlling a camera remotely has long been a source of concern to privacy advocates, conventional wisdom said there was at least no way to deactivate the warning light. New evidence indicates otherwise.

Marcus Thomas, former assistant director of the FBI's Operational Technology Division in Quantico, said in a recent story in The Washington Post that the FBI has been able to covertly activate a computer's camera — without triggering the light that lets users know it is recording — for several years.

Now research from Johns Hopkins University provides the first public confirmation that it's possible to do just that, and demonstrates how. While the research focused on MacBook and iMac models released before 2008, the authors say similar techniques could work on more recent computers from a wide variety of vendors. In other words, if a laptop has a built-in camera, it's possible someone — whether the federal government or a malicious 19 year old — could access it to spy on the user at any time.