Hardware Microphone Disconnect in Mac and iPad
They do not reveal how this is implemented at the physical level. I'd think such a statement should be accompanied by a circuit diagram.The simplest and most fool proof method is a physical switch that interrupts the mic lead. If you want it to be 'pop and crackle' free you may have to fiddle a bit or use a make-before-break switch and connect the other line to ground. No amount of software hacking will get around that, and the position of the switch is good feedback that you are not open to eavesdropping. Anything less than that is likely hackable in some way or other.