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Simtel MSDOS 1992 September
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Simtel20_Sept92.cdr
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trojanpr
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TRECOVER.DD
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1989-12-16
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7KB
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138 lines
------------------------------------------------------------------
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| TROJAN HORSE RECOVERY |
| |
------------------------------------------------------------------
| Issue #9: December 17, 1989 |
| Revision Stage: C |
| |
| Written by Eric Newhouse |
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While reading this, bear in mind that there is no better remedy
for a drive that has run a trojan horse than a recent backup..
AARGH! Perhaps your hard disk sounds like a sick moose. Perhaps
your drive light starts flashing repeatedly, like a police car's
lights. Perhaps your drive just sits in the computer, and the
computer doesn't acknowledge its presence.
Having watched my drive crash many times, I can understand the
frustration you will feel after your hard disk conks out. While a
faulty hard drive, disk controller, or cable can make these
ailments uncurable without spending a lot of money, usually you
CAN recover from a trojan horse with only investing a little time.
After running a trojan horse, the first thing to do is calm down.
Face the situation stoicly; it may prevent your hair from turning
gray. Diagnose the damage. Was your [hard] drive formatted?
Did the trojan scramble your FAT table? Did it erase every file?
Did it erase or format your [hard] drive's boot sector? The odds
are that the trojan incurred one of these four disasters.. After
a successful diagnosis, you are ready to remedy the problem.
1) If the trojan low-level formatted your [hard] disk:
Hope that you have a recent backup; that's the only remedy
for this disease.
2) If the trojan high-level formatted your [hard] disk:
In 1987 Paul Mace introduced a way to recover formatted
data. Unfortunately, most programs can only recover
formatted data COMPLETELY if you run a "snapshot" program
right before the format. The reason: DOS fragments large
files and without an accurate map of the formatted disk,
unformatters have problems dealing with such files. You
will need one of these three programs to recover your disk
if the trojan formatted it:
1. PC-Tools Deluxe (Central Point, $79.95)
2. Mace+ Utilities/Gold (Paul Mace $99.95)
3. Advanced Norton Utilities (Peter Norton, $150.00)
retail)
There is at least one other program that can unformat
disks, but the name of it is slipping my mind. As of this
printing, PC-Tools probably has the best unformatter. It
can reputedly reconstruct formatted disks regardless of
the disk's state of fragmentation. PC-Tools may not be
right for your other disk management needs, however, so
you should talk to a salesmen about these products before
making a purchase.
3) If the trojan scrambled your FAT table:
Sector editors such as those included in the Norton
Utililites, PC-Tools, and a host of other popular utility
packages (not Mace+) allow experienced users to piece
their FAT backtogether from Gibberish. This avenue of
recovery is only open to extremely proficient users,
however. Everyone else, including myself, must rely on a
FAT backup program to provide a feeling of security.
DBACK10.ZIP (available on my board) will back up your FAT
table in under a minute to floppy. DBACK makes FAT
backup easy and non time consuming.
4) If the trojan erased file(s), and the FAT table is
undamaged:
There are many commercial and public domain packages
available that undelete deleted files. Norton Utilities,
PC-Tools, MACE+, and UNDEL.COM will all do the job. The
commercial products are all more reliable in undeleting,
but they are also more expensive that the Public-Domain
UNDEL. Always undelete your most recent files first; that
is, undelete files in the order of last time written to
disk. I know that PC-Tools and Mace automatically list
undeletable files in the correct order, but the other
two may not.
5) If the boot sector on your hard disk gets
erased/formatted:
There are four things to do if this happens, and the
worst that can happen is that you will go without a hard
disk for a while. Backup before proceeding with any of
the steps here, for you may have to destroy some files to
restore your hard disk to boot status.
A) Try doing a "SYS C:" (or "SYS A:") from your
original DOS disk. Then copy COMMAND.COM back onto
the hard drive. If your hard drive still won't boot
then try step B.
B) If you have the MACE+ utilities go to the "other
utilities" section and "restore boot sector." This
should do the job if you have been using MACE+
correctly.
C) If you are still stuck, BACK EVERYTHING UP and
proceed to do a low level format. Instructions on
how to perform a low-level format should come with
your hard disk controller card. Be sure to map out
bad sectors using either SCAV.COM by Chris Dunford
or by manually entering the locations of bad sectors
into the low level format program. After the low
level format run FDISK.COM (it comes with DOS) to
create a DOS partition. Refer to your DOS manual
for help in using FDISK. Then put your original DOS
diskette in drive A: and type FORMAT <drive
letter>:/S/V. <Drive letter> represents the letter
of the disk you are formatting. Try rebooting
again.
D) If you are still stuck, either employ some
professional computer repairmen to fix your drive,
or live with a non-bootable hard drive..
Mace+/Gold, PC-Tools, and Norton's Utilities are all fine
programs. However, there's one more program worth mentioning, and
that's SpinRite (tm) by Steve Gibson. SpinRite advertises itself
by saying that it prevents ALL hard disk crashes before they
happen. I don't have any experience with the program, but I know
some colleagues who love it. SpinRite may be worth a look.