This virus was found in the end of 1993 in France, and later that
year it was in the wild in Denmark. During 1994 reports of this
virus has been received from almost all countries in Europe.
Jumper infects diskette boot sectors and hard disk MBRs in the
usual manner. It infects hard disks only if the user tries to
boot from an infected diskette. If the hard disk is infected the
virus infects diskettes that are used in the computer. Not all
diskettes will be infected, though.
Unlike most other boot sector viruses, Jumper doesn't hook the
disk interrupt (INT 13h) at all; instead, it hooks INT 21h and
INT 1Ch. Due this, Jumper is able to spread also under OS/2 or
Windows 95, unlike most other boot viruses.
The virus will sometimes hang the machine when it's booted from
a hard drive and will display graphical characters on the screen.
There exists also a slightly modified B variant. The virus has
several alias names.
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