In addition to releasing Mac OS X 10.1.2 tonight, Apple also posted an update to its Open Firmware Password application. The application allows you to set security features on your computer.
By enabling the security features in firmware you can prevent the computer from being starting using a volume other than the one you chose as the startup disk. This means you cannot startup from other devices such as an external FireWire disk, a CD-ROM drive or another partition or disk inside the computer.
Enabling the security features also disables all keys that affect the normal startup of the computer, except the option key. You can hold down the option key at boot to choose another startup volume; you will be asked for your firmware password before you can choose another disk.
Open Firmware Password 1.0.2
requires Firmware update 4.1.7 or a later version and Mac OS X 10.1 or later.