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CERT* Summary CS-98.02 - SPECIAL EDITION
March 4, 1998
This special edition of the CERT Summary reports denial of service attacks
targeting a vulnerability in the Microsoft TCP/IP stack.
Past CERT Summaries are available from
ftp://ftp.cert.org/pub/cert_summaries/
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Denial of service attacks targeting Windows 95/NT machines
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This special edition of the CERT Summary reports denial of service attacks
targeting a vulnerability in the Microsoft TCP/IP stack. We have received
reports from a number of sites and incident response teams indicating that a
large number of machines were affected.
The attacks involve sending a pair of malformed IP fragments which are
reassembled into an invalid UDP datagram. The invalid UDP datagram causes the
target machine to go into an unstable state. Once in an unstable state, the
target machine either halts or crashes. We have received reports that some
machines crashed with a blue screen while others rebooted.
Attack tools known by such names as NewTear, Bonk, and Boink have been
previously used to exploit this vulnerability against individual hosts;
however, in this instance, the attacker used a modified tool to automatically
attack a large number of hosts.
The solution to protect Windows 95 and NT machines from this attack is to
apply the appropriate Microsoft patch. The Microsoft patch, as well as more
information about the vulnerability, can be found in the January 1998
Microsoft Market Bulletin entitled, "New Teardrop-like TCP/IP Denial of
Service Program" available from:
http://www.microsoft.com/security/newtear2.htm
Although the first instance of this attack, which started March 2, 1998
appears to be over, keep in mind that the tools to launch this attack are now
available and we expect to see more incidents of this type.
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How to Contact the CERT Coordination Center
Email This email address is being protected from spambots. You need JavaScript enabled to view it.
Phone +1 412-268-7090 (24-hour hotline)
CERT personnel answer on business days
8:30-5:00 p.m. EST (GMT-5)/EDT(GMT-4),
and are on call for emergencies during
other hours.
Fax +1 412-268-6989
Postal address
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
USA
To be added to our mailing list for CERT advisories and bulletins, send your
email address to
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In the subject line, type
SUBSCRIBE your-email-address
CERT advisories and bulletins are posted on the USENET news group
comp.security.announce
CERT publications, information about FIRST representatives, and other
security-related information are available for anonymous FTP from
http://www.cert.org/
ftp://ftp.cert.org/pub/
If you wish to send sensitive incident or vulnerability information to CERT
staff by electronic mail, we strongly advise you to encrypt your message.
We can support a shared DES key or PGP. Contact the CERT staff for more
information.
Location of CERT PGP key
ftp://ftp.cert.org/pub/CERT_PGP.key
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Copyright 1998 Carnegie Mellon University. Conditions for use, disclaimers,
and sponsorship information can be found in
http://www.cert.org/legal_stuff.html and ftp://ftp.cert.org/pub/legal_stuff .
If you do not have FTP or web access, send mail to This email address is being protected from spambots. You need JavaScript enabled to view it. with
"copyright" in the subject line.
* CERT is registered in the U.S. Patent and Trademark Office.
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