More Diligent Measures, Even Hardware Removal
This is an advanced topic.
To “harden” a system, more diligent measures must be taken, such as physically removing Airport and Bluetooth wireless capabilities, removing the iSight camera, removing kernel extensions so as to disable various functionality, disabling certain commands, etc.
Such measures will not be acceptable to many users.
For more on such measures, see the National Security Agency’s (NSA) Hardening Tips for Mac OS X Snow Leopard.