4.2. BIOS and Boot Loader Security

Password protection for the BIOS (or BIOS equivalent) and the boot loader can prevent unauthorized users who have physical access to systems from booting using removable media or attaining root privileges through single user mode. But the security measures one should take to protect against such attacks depends both on the sensitivity of the information the workstation holds and the location of the machine.
For instance, if a machine is used in a trade show and contains no sensitive information, than it may not be critical to prevent such attacks. However, if an employee's laptop with private, unencrypted SSH keys for the corporate network is left unattended at that same trade show, it could lead to a major security breach with ramifications for the entire company.
On the other hand, if the workstation is located in a place where only authorized or trusted people have access, then securing the BIOS or the boot loader may not be necessary at all.

4.2.1. BIOS Passwords

The following are the two primary reasons for password protecting the BIOS of a computer[5]:
  1. Preventing Changes to BIOS Settings — If an intruder has access to the BIOS, they can set it to boot from a diskette or CD-ROM. This makes it possible for them to enter rescue mode or single user mode, which in turn allows them to start arbitrary processes on the system or copy sensitive data.
  2. Preventing System Booting — Some BIOSes allow password protection of the boot process. When activated, an attacker is forced to enter a password before the BIOS launches the boot loader.
Because the methods for setting a BIOS password vary between computer manufacturers, consult the computer's manual for specific instructions.
If you forget the BIOS password, it can either be reset with jumpers on the motherboard or by disconnecting the CMOS battery. For this reason, it is good practice to lock the computer case if possible. However, consult the manual for the computer or motherboard before attempting to disconnect the CMOS battery.

4.2.1.1. Securing Non-x86 Platforms

Other architectures use different programs to perform low-level tasks roughly equivalent to those of the BIOS on x86 systems. For instance, Intel® Itanium™ computers use the Extensible Firmware Interface (EFI) shell.
For instructions on password protecting BIOS-like programs on other architectures, refer to the manufacturer's instructions.

[5] Since system BIOSes differ between manufacturers, some may not support password protection of either type, while others may support one type but not the other.