About Firmware Passwords
To protect the data on your Mac, you can set a user account password to prevent unauthorized users from logging in. You can also encrypt your startup disk using FileVault so that unauthorized users can't read the data stored on your Mac without the right password.
For additional protection, you can also set a firmware password on your Mac. A firmware password prevents your Mac from starting up from any device other than your designated startup disk.
You can set a firmware password on these Macs:
MacBook Air (Late 2010 and later) MacBook Pro (Early 2011 and later) MacBook Pro with Retina display (all models) MacBook (Retina, 12-inch, Early 2015) iMac (Mid 2011 and later) Mac mini (Mid 2011 and later) Mac Pro (Late 2013)