MBR

Short for Master Boot Record, MBR is also sometimes referred to as the master boot block, master partition boot sector, and sector 0. The MBR is the first sector of the computer hard drive that tells the computer how to load the operating system, how the hard drive is partitioned, and how to load the operating system.
In the above picture, is an example of what a partitioned hard drive may look like. In this case, the MBR is the first section of the hard drive the computer looks at after the BIOS hands control to the first bootable drive. Unlike the VBR, there is always only going to be a maximum of one MBR on a partitioned hard drive.
An MBR virus is a common type of virus that replaces the MBR with its own code. Since the MBR executes every time a computer is started, this type of virus
 is extremely dangerous. MBR viruses normally enter a system through a floppy disk that is installed in the floppy drive when the computer is started up.
Even if the floppy disk is not bootable, it can infect the MBR
the Stone Empire Monkey Virus is an example of a MBR virus.