The biggest risk to your Mac is if it is lost, stolen or physically compromised. If you setup a secure password as discussed previously and the thief can’t login, they can still gain access to all your data using one of the special start-up modes built into all Macs.
These start-up modes include booting from an install DVD and resetting the password, using Target Disk Mode to use your Mac as an external hard disk, or booting into Unix-style Single User Mode.
There is a way to protect your computer by setting a firmware password. The password is written into the computer’s firmware chips on the motherboard and if anyone tries to use a special start-up mode, they will be prompted for that password.
Apple provides a utility for setting a firmware password called Firmware Password Utility.
For Mac OS X 10.5.x, start from the Leopard Install DVD and choose Firmware Password Utility from the Utilities menu.
1. Click to select the checkbox for “Require password to change Open Firmware settings”, as shown below.
2. Type your password in the Password and Verify fields.
3. Click OK
4. Click lock icon to prevent further changes
5. Choose Quit from the application menu
Now, if anyone attempts to use any of the special start-up modes, they will be prompted for the firmware password you set.