How to disable macbook's mic, but not speakers?

I found this informative post about completely disabling audio on OS X by removing/disabling the required audio kernel extensions. The problem is this disables audio-in and audio-out, and I only want to disable audio-in.

I'm looking to completely disable audio-in, in a way which cannot be re-enabled by unprivileged users, not just muting it. How could I accomplish this?

Disabling Input

To disable the input, I'm not entirely sure. Here's what I thought of:

• You can use a internal audio input device like SoundFlower, which basically routes the audio output into the audio input.
• You can mute the volume (although you said you don't want to do only that)
• You could take a look around the /System/Library/Extensions/ folder and in the IOAudioFamily.ktexts file for anything useful, however that can muck up OS X.

Preventing Changes

Disabling underprivileged users from changing the settings isn't actually too hard:

$ sudo chmod 700 /System.Library/PreferencePanes/Sound.prefPane

Will do the trick. Loading the preference pane from any user (other than root) will display an error.