While it certainly is recommended to use a login password for your Mac, this does not prevent someone from being able to access the data on your hard drive. For instance,someone could attach an external drive containing Mac OS X to your computer and then boot from it, thus bypassing the startup disk’s login password.
You can prevent this from occurring by establishing a firmware password. What this does, is requires a password to use the different disk as the startup volume. Luckily, it is quite easy to set a firmware password in Lion. Note that if you established a firmware password in Snow Leopard and upgraded to Lion, the password is no longer valid. You will need to create a new one.
To Set a Firmware Password
- Restart the computer, holding down the Command and R keys during boot up. This will boot you to the Recovery System.
- If prompted, select the language you want the Recovery Partition to use.
- Click Utilities from the menu and then click Firmware Password Utility from the menu.
- From the dialog box, click the Turn on Firmware Password button.
- Enter the password you wish you use. You will need to type it in twice to verify it.
- Click OK and restart your computer.
The next time you try to boot from a disk other than your computer’s hard drive, a lock icon appears on the screen with a text box underneath, into which you must enter a password (your firmware password) before being able to progress further. You will also be required to enter in your firmware password if you try to boot into the Recovery System (Command and R).