[zeta0134]

Right, but having a dummy plug will cause the vast majority of laptops to disable their built-in microphones and instead listen to whatever you plugged in. (In the case of a dummy, this would result in a dead line.)

The idea is to fool the system into having no physical microphone, and even a hacker/malware that compromises the operating system is going to have a hard time dealing with whatever soundcard firmware is responsible for making that switch in the hardware.