[zamnos]

Nothing can beat a physical switch but even if it's solid state, unless it's in the CPU itself (it isn't) there still need to be traces in/on the PCB to bring the data from the microphone to the rest of the system, so just probe those traces when the lid is open vs closed. Or learn how to decap chips. There are some really awesome videos out there about that on YouTube!

More importantly though, Apple learned their lesson with the iSight which had a software-based activation LED. They assumed a random script kiddie wouldn't have the smarts to be able to hack the kext kernel module to turn the camera on without also turning the LED on. Unfortunately they learned about the Internet shortly thereafter where random script kiddies were able to get instructions on how to modify that kext, leading to some embarrassing moments, for some (possibly naked) high school teens, and for Apple.

Thats why the linked article is very careful to specifically mention that even having root and being able to manipulate kexts is not enough to silently use the microphone while closed.

https://news.ycombinator.com/item?id=35059224