(
Basic
Input/
Output
System attack) An unauthorized alteration of the BIOS in a PC. Since BIOS routines are run when the computer is booted, any malware executed at that stage takes complete control of the computer even before the operating system is loaded. In the days of the read-only ROM BIOS, no changes could be made; however, the flash-based BIOS is updatable. See
flash BIOS.