Brain (World's first Computer Virus)

©Brain (the industry standard name being Brain) is (in its first incarnation written in January 1986) considered to be the first computer virus for MS-DOS. It infects the boot sector of storage media formatted with the DOS File Allocation Table (FAT) file system. The virus is also known as Lahore, Pakistani, Pakistani Brain, Brain-A and UIUC.Businessweek magazine at the time called the virus the Pakistani flu.

http://en.wikipedia.org/wiki/Brain_(computer_virus)