You can enable a Mac webcam without warning lights being turned on. Researchers from John Hopkins University (JHU) have discovered an exploit in the firmware of older Mac’s called iSight. This firmware can be modified to allow the camera to be enabled while the indicator light remains off.
Researchers at JHU have found a way to reprogram the STANDBY pin to remain in the STANDBY status even when the image sensor is active. They have taken the existing iSight firmware and modified it then reprogrammed the camera that uses a vendor-specific method of USB device requests from the host operating system (OS). The scary part about this attack is that it does not require elevated privileges.
The JHU researchers have developed an application that can be ran on any Mac computer. It will automatically detect if the firmware is vulnerable. If it is while the program is running you will be able to enable and disable the LED at your leisure. Once the application is closed the original firmware will be reloaded and perform normally. The JHU researchers have released this white paper to explain in depth their findings.
This software does have one more trick, if running in a virtual machine (VM), the application can escape the VM and attack the host OS. This is a particularly dangerous attack. This can allow malicious software that would have normally been contained to run rampant on any host OS.
The JHU researchers are working both sides of the fence. They have discovered the vulnerability and created great firmware to exploit this vulnerability, but they have also created defensive software. iSightDefender was developed by JHU since Apple could not resolve this on their own. This application blocks specific USB device requests that may be used to load rouge firmware.