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>>                                                      CERT-NL, 01-Mar-2000 <<
>> All CERT-NL information has been moved to http://cert.surfnet.nl.  Links  <<
>> to CERT-NL information contained in this advisory are therefore outdated. <<
>>                                                                           <<
>> CERT-NL also has stopped the CERT-CC-Mirror service.  Due to this the     <<
>> links to the CERT-CC mirror are obsolete. Visit the CERT-CC site for the  <<
>> complete CERT-CC advisory texts:                     http://www.cert.org  <<
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Security Advisory                                                       CERT-NL
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Author/Source : Don Stikvoort (CERT-NL)                     Index  :    S-92-22
Distribution  : SURFnet constituency                        Page   :          1
Classification: External                                    Version:      Final
Subject       : destructive CHKDSK bug in some DOS versions Date   :  10-dec-92
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CERT-NL received word (through FIRST) from John Carr and Chris Baxter of CCTA
London about a rather nasty, potentially destructive, bug in CHKDSK apparent 
in MS-DOS and PC-DOS versions 4 and 5.0 shipped before 11 nov 91. Please take
notice and warn your users if needs be.

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Citation: warning by Carr and baxter, CCTA 
*******************************************************************************

...
a problem with CHKDSK in MS-DOS and PC-DOS
versions 4 and 5.0 shipped before 11 November 1991.

It seems that if you have a 256 sector File Allocation Table (FAT), which 
occurs with certain large partition sizes - 128, 256, 512, 1024 MB, this
version of CHKDSK will overwrite the first 32 MB of your disk if used with
/Fix option.

This is a problem which would not have been noticed initially, but which will
get worse as people upgrade their disks. At the moment I suspect that mainly
Network file servers are at risk.

IBM and Microsoft know about the problem - it is documented as Q80496 on the
Microsoft knowledge base, but not many users seem to know of it! I suspect 
that if users encounter the problem, they will blame it on a suspect disk,
since they will be trying to mend it at the time.

CCTA has alerted its constituency in the UK government to the problem and has
advised that all PCs be upgraded to MS-DOS 5.0A  or PC-DOS 5.01, with those
most at risk being done first. It is very important for small systems and
maintenance groups to be aware of this problem.

...
 
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End of citation.

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CERT-NL is the Computer Emergency Response Team for SURFnet customers. SURFnet
is the Dutch network for educational, research and related institutes. CERT-NL
is a member of the Forum of Incident Response and Security Teams (FIRST).

All CERT-NL material is available under:
  http://cert.surfnet.nl/

In case of computer or network security problems please contact your local
CERT/security-team or CERT-NL  (if your institute is NOT a SURFnet customer
please address the appropriate (local) CERT/security-team).

CERT-NL is one/two hour(s) ahead of UTC (GMT) in winter/summer,
i.e. UTC+0100 in winter and UTC+0200 in summer (DST).

   Email:     cert-nl@surfnet.nl     ATTENDED REGULARLY ALL DAYS
   Phone:     +31 302 305 305        BUSINESS HOURS ONLY
   Fax:       +31 302 305 329        BUSINESS HOURS ONLY
   Snailmail: SURFnet bv
              Attn. CERT-NL
              P.O. Box 19035
              NL - 3501 DA  UTRECHT
              The Netherlands

NOODGEVALLEN:    06 22 92 35 64      ALTIJD BEREIKBAAR
EMERGENCIES : +31 6 22 92 35 64      ATTENDED AT ALL TIMES
CERT-NL'S EMERGENCY PHONENUMBER IS ONLY TO BE USED IN CASE OF EMERGENCIES:
THE SURFNET HELPDESK OPERATING THE EMERGENCY NUMBER HAS A *FIXED*
PROCEDURE FOR DEALING WITH YOUR ALERT AND WILL IN REGULAR CASES RELAY IT
TO CERT-NL IN AN APPROPRIATE MANNER. CERT-NL WILL THEN CONTACT YOU.
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