BIOS or Firmware Password Protection
Pre-boot authentication (PBA) or power-on authentication (POA) serves as an extension of the BIOS or boot firmware and guarantees a secure, tamper-proof environment external to the operating system as a trusted authentication layer. The PBA prevents anything being read from the hard disk such as the operating system until the user has confirmed they have the correct password or other credentials
Windows and Mac Computers have the ability to add a Password at Start UP. This password can prevent unauthorized access to the computer. It can prevent a person from Starting up off alternate hard drives, usb sticks, Network Boot drives. These are ways to start a computer and gain access to the data on the hard drive and by pass the security of the operating System in some cases.