Of course, the opposite of a password that keeps you out of your system is a password that keeps others out of your system. The BIOS in some PCs may provide no password protection at all, a single password that controls access to BIOS setup and allows the system to boot up, or two passwords—one for access to BIOS setup (a Setup or Supervisor password) and bootup, and the other to control access to booting up only (a User or Boot password). To set a password for your system, look in the setup menus for security settings. A User or Boot password keeps the system from booting up—a measure of intrusion and system hacking protection. A System or Supervisor password keeps lurkers out of your BIOS settings, and keeps them from changing the User/Boot password. If you are going to set a User or Boot password, be sure you also set a Setup or Supervisor password so the BIOS settings and boot password cannot be changed and so someone cannot set a Supervisor password to keep you out of the system, requiring you to bypass the BIOS password . Because there is a back door, the only way to prevent attackers from circumventing the password is to use a case that can be locked shut with a key or a locking cable.