SSCRC.EXE Program Documentation V1.4 April, 1988 (c) OSR

What does SSCRC do?

SSCRC.EXE is a program which generates and uses a data file
containing the 16 bit CRC's of each and every file on a
particular disk drive. Directories and sub-directories are
traversed in turn, none are missed.

What use is it to me?

Having calculated and recorded the CRC for every file on your
hard disk, it is then possible to run SSCRC in checking mode to
determine whether ANY file on your hard disk has changed in
either size or content since the original SSCRC data file,
'ACRC.CRC', was created. You are notified of changes on the
screen and by a written record of changes in the file REPORT.CRC.

So what?

Well, a 16 bit CRC file calculation is a very very reliable
method for detecting whether a file has been altered, either by
accident, by a hard disk or program failure, or deliberately, by
a "VIRUS".

How do I use this thing?

Run SSCRC/F (build a new checking file) once a month or so, or
when you change the contents of your hard disk significantly.

Run SSCRC/C (check files) every morning or once a week. Have a
careful look at the resulting file, REPORT.CRC, to be found in
the ROOT DIRECTORY. Many files will have changed because you have
caused a change. For example, a document you edit will cause a
change in the CRC value. If you alter the setup of a program, a
CONFIG file will probably change. File changes like this are
nothing to worry about. Run SSCRC/F to re-build the ACRC.CRC data
file if you want these changes recorded.

IF you find, by viewing the REPORT.CRC file, that files such as
COMMAND.COM, ANSI.SYS, IBMDOS.COM etc have changed, then
something is very wrong. Generally, if you find that your EXE
files are changing, it is time to start worrying about a "VIRUS".
As a general rule, EXE and COM file shouldn't change. The
EXECEPTION to these rules are packages which store their setup
information in the actual EXE file when you change display type
or printer type.

The MAIN USE for SSCRC is when you run CHKDSK/F and find LOST
chains. Usually, these 'LOST CLUSTERS' come from deleted files,
however, sometimes, due to a program crash etc, other files may be
corrupted. RUN SSCRC/C to see if any of your active files have
been altered.

The whole point of SSCRC is that if CRC's match over a period of
time for a particular file, you may be SURE that the file HAS NOT
BEEN ALTERED. It is virtually impossible to alter a file, either
malicously or by accident, and maintain the same CRC.

Performance Notes

SSCRC reads 32k bytes at a time using a DOS call, (not C read()
). The CRC is calculated using the lookup table method, much
faster than the usual iterative technique. Note that the CRC is
the standard CCITT CRC, not the popular XMODEM-CRC, which is
mildly brain-damaged.


The following comes from the help screens of SSCRC.EXE:

SSCRC.EXE has two functions:

SSCRC /F 1) Build a CRC file (ACRC.CRC) of all files on a drive
including all sub-directories.

SSCRC /C 2) Use ACRC.CRC generated by 1) to check the integrity and
existence of the files recorded in ACRC.CRC. This
function writes REPORT.CRC to the root directory
detailing file corruptions and updates.

The intention of this utility as a confidence test of all files on all your
hard disk and floppy disks.

If SSCRC says the file hasn't changed you may be sure that the file has not
been altered in any way (99.9999% sure anyway). Files which are missing
from the original ACRC.CRC are also reported, whole directories which have
been deleted are also reported.

Suggested operation is to run `SSCRC /F' about once a month. If you ever have
any doubts about the integrity of your file system, run 'SSCRC /C'.

The SSCRC /F option maybe replaced by SSCRC [start path] /F. For example,
,if you only wanted to build a CRC file starting at 'D:\LOTUS', SSCRC would
begin build an ACRC.CRC with D:\LOTUS and any sub-directories attached to
your Lotus directory:

SSCRC D:\LOTUS /F

Note: the direcory spec must come BEFORE the '/F' command. SSCRC /C will
only check files in your LOTUS directory and attached sub-directories.


What we want from YOU

SSCRC is 'Low-Cost' Shareware, if you use this utility to protect
your system, do the right thing and send us $10. It will only
take a few minutes to write a cheque and post it.

If you think SSCRC is rubbish, don't clutter your hard disk,
delete it now. Consider writing us a short note telling us why
you think its of no use to you.

If you don't feel that shareware is worth paying for then don't
be suprised if you see your next 'must have' program in a shop
for $299 instead of on a bulletin board for free (or $10).

Address: OSR
561 Blaxland Rd
Eastwood, 2122, NSW
AUSTRALIA


End of SSCRC Documentation, April, 1988 (c) OSR