[comp.virus] Mutation of Stoned/Implications for self check

PHYS169@csc.canterbury.ac.nz (Mark Aitchison, U of Canty; Physics) (04/02/91)

CHESS@YKTVMV.BITNET (David.M.Chess) writes:

> ... Someone that I trust to be reasonably knowledgeable
> in such things told me awhile back something like (I didn't write it
> down) this: some hard disk controllers keep some information about the
> structure of the hard disk on the hard disk itself, in the MBR.

An area, up to 17 bytes, before the partition table, is used by some
older XT controllers to store disk type parameters, instead of using
CMOS or jumpers.*

This isn't a problem for sensible checkers, since the area cannot gain
control (even if it does contain nasty stuff), so long as the rest of
the sector is still okay. The IMMUNISE program works around that area,
for example.

Mark Aitchison, Physics, University of Canterbury, New Zealand.
* Info courtesy of Peter Johnson, still half asleep when I phoned.