[comp.virus] Software boot protection

SANTO@SENECA.BITNET (12/11/90)

In response to CON_JDC@SELWAY.UMT.EDU's query about boot protection:

We have a package called Protec which includes software boot
protection. It is good against users trying to do damage to the hard
disk intentionally.  However, an advanced user who wants to do some
real harm can do a low-level format quite easily. Regarding virus
protection, when a student boots from a floppy and tries to access the
hard disk, an "Invalid drive specification" message is shown. It does
everything that was stated in your message, EXCEPT, it does not
protect against most computer viruses.

Two viruses which I have seen infect a Protec'ted hard disk include
the Stoned and the Ping Pong B virus. Both of these boot sector
viruses infect the hard disk and I would assume any other boot
sector/partition table virus would do the same. The hard disk,
however, would be protected from COM and EXE infecting viruses since
DOS doesn't know that the hard disk is there.

When booting from a "Stoned" infected floppy diskette, the virus in
fact disappears. It is not present in the hard disk partition table. I
have not checked to see if this virus stays memory resident. I do know
that he Stoned virus was definitely there because physical sector 7
contains the original partition table, an effect of infecting the hard
disk. I suspect that there are two partition tables and that the
appropriate one is selected when booting from a hard disk or a floppy.

The Ping Pong virus does something totally different. When booting
from a "Ping Ponged" diskette, the virus gets copied to the boot
sector et cetera like normal. Trying to boot from the hard disk later,
the machine is unable to boot.  If you try to boot and then put in any
number of floppy diskettes, the diskettes will all become infected. If
you boot from a clean floppy you can access the hard disk but the
volume label shows garbage and a FAT error occurs (some major side
effects!). Cleaning the hard disk will restore everthing to normal.

I'm not a DOS expert and maybe someone can explain to me why these
things are happening but I figure the virus doesn't care if drive C:
is a DOS disk or not. Because of the boot protection, anything should
think that the hard disk is not there except for software manipulating
physical sectors. A low-level format and Norton Utilities can both see
the hard disk. I would assume that viruses read and write physical
sectors.

This is not a direct response to your question but rather an overview
of what happens when boot protection is employed.

Hope this helps.

Santo Nucifora
SANTO@SENECA.BITNET