One of the ways we would be able to tell that our webcams are active, regardless whether used as a microphone or as a webcam, would be a light on the device that basically lets us know that it is on. Unfortunately it would seem as though there are ways to go around disabling that, as researchers from the John Hopkins University have shared in which they demonstrated how hackers are able to remotely control MacBook iSight cameras without alerting the user, namely due to their ability to disable the LED indicator light.
According to the report, “We describe how to disable the LED on a class of Apple internal iSight webcams used in some versions of MacBook laptops and iMac desktops […] This enables video to be captured without any visual indication to the user and can be accomplished entirely in user space by an unprivileged (non- root) application.” This is accomplished by reprogramming the camera’s micro-controller, from which they were able to turn on the webcam separately from the light.
The semi-good news is that the hack affects older MacBook computers up to 2008’s models, include the iMac G5, so if you’re a new owner of a MacBook Air/Pro or iMac, you can rest easy, but if you want to be safe, you could always place a tape over the iSight camera when not in use.