h4k.com

Installing Apple Open Firmware adds an additional layer of protection to an Apple computer by requiring a password to be entered before accessing one of the many potentially compromising start-up options This password can be removed by anyone with physical access to the computer by resetting a section of memory called the PRAM.

1) Change the amount of memory in the computer by adding or removing a stick of memory.
2) Turn the computer on.
3) Hold down Command, Option, ‘p’, and ‘r’ at the same time until the computer beeps and reboots three times. The password has now been removed.

To prevent this attack the Apple computer needs to have access to the memory physically locked and secured.