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TUCoPS :: Windows Net Apps :: ciaci080.txt

Microsoft Exchange DoS Attacks



                       The U.S. Department of Energy
                    Computer Incident Advisory Capability
                           ___  __ __    _     ___
                          /       |     /_\   /
                          \___  __|__  /   \  \___

                             INFORMATION BULLETIN

                 Microsoft Exchange Denial of Service Attacks

August 5, 1998 22:00 GMT                                          Number I-080
PROBLEM:       Vulnerabilites have been identified in the Exchange Internet
               Mail Service (IMS), the service that handles the SMTP protocol,
               and the Information Store, the service that handles the NNTP
PLATFORM:      Microsoft Exchange Server 5.0 and 5.5.
DAMAGE:        If exploited, an attacker may be able to cause a Denial of
SOLUTION:      Apply hotfixes. If you cannot apply the hotfix immediately,
               Microsoft recommends that you configure the Server Monitor in
               Microsoft Exchange Server Administrator to automatically
               restart the affected services if they stop.
VULNERABILITY  An attacker can disrupt an organization by crashing a Microsoft
ASSESSMENT:    Exchange Server over the network. This attack will stop e-mail
               and other services that Exchange provides for the organization.

[ Start ISS Security Advisory ]

ISS Security Advisory
July 24, 1998

Denial of Service attacks against Microsoft Exchange 5.0 to 5.5


An attacker can disrupt an organization by crashing Microsoft Exchange
Server over the network.  This attack will stop e-mail and other services
that Exchange provides for the organization.

Recommended Action:

Install vendor supplied hotfixes for Microsoft Exchange 5.0, and 5.5.
Hotfixes are available for Exchange 5.0 and 5.5 at the following locations:

Exchange Server 5.0 ALL LANGUAGES:

Exchange Server 5.5 ENGLISH:

Exchange Server 5.5 FRENCH:

Exchange Server 5.5 GERMAN:

Exchange Server 5.5 JAPANESE:

If you cannot apply the hotfix immediately, Microsoft recommends that you
configure the Server Monitor in Microsoft Exchange Server Administrator to
automatically restart the affected services if they stop.

Determining if you are vulnerable:

If you are running Microsoft Exchange 5.0 or 5.5 without appropriate
hotfixes, you are vulnerable to the attacks.


There are vulnerabilities in the Exchange Internet Mail Service (IMS), the
service that handles the SMTP protocol, and the Information Store, the
service that handles the NNTP protocol, that will allow an attacker to
crash the Internet Mail Service or the Information Store. These
vulnerabilities are related to the way that the IMS handles the AUTH
command and how the Information Store's NNTP server handles AUTHINFO. Both
of these systems experience buffer overflow issues.

A similar problem not related to the buffer overflow issue involves how IMS
handles the AUTH command. This issue will also cause the service to crash.

Note that when the Internet Mail Service crashes, the rest of Microsoft
Exchange will still operate. When the Information Store crashes, Exchange
Server cannot operate.

Vulnerable Versions:

Microsoft Exchange Server 5.0 and 5.5 are vulnerable without hotfixes

Additional Information:

There are two Microsoft Knowledge Base articles that address these issues
- -- Q188369 and Q188341. These can be obtained from Microsoft Support Online
at ISS X-Force thanks the Microsoft Exchange
group for providing assistance and patches to these issues in a timely

These security issues were discovered by Jon Larimer of ISS X-Force

- --------

Copyright (c) 1998 by Internet Security Systems, Inc.

Permission is hereby granted for the redistribution of this Alert
electronically.  It is not to be edited in any way without express consent
of X-Force.  If you wish to reprint the whole or any part of this Alert in
any other medium excluding electronic medium, please e-mail
for permission.


The information within this paper may change without notice. Use of this
information constitutes acceptance for use in an AS IS condition. There are
NO warranties with regard to this information. In no event shall the author
be liable for any damages whatsoever arising out of or in connection with
the use or spread of this information. Any use of this information is at
the user's own risk.

X-Force PGP Key available at: as
well as on MIT's PGP key server and's key server.

X-Force Vulnerability and Threat Database:

Please send suggestions, updates, and comments to:
X-Force <> of Internet Security Systems, Inc.

- --------------

[ End ISS Security Advisory ]

CIAC wishes to acknowledge the contributions of Internet Security Systems,
Inc. for the information contained in this bulletin.

CIAC, the Computer Incident Advisory Capability, is the computer
security incident response team for the U.S. Department of Energy
(DOE) and the emergency backup response team for the National
Institutes of Health (NIH). CIAC is located at the Lawrence Livermore
National Laboratory in Livermore, California. CIAC is also a founding
member of FIRST, the Forum of Incident Response and Security Teams, a
global organization established to foster cooperation and coordination
among computer security teams worldwide.

CIAC services are available to DOE, DOE contractors, and the NIH. CIAC
can be contacted at:
    Voice:    +1 925-422-8193
    FAX:      +1 925-423-8002
    STU-III:  +1 925-423-2604

For emergencies and off-hour assistance, DOE, DOE contractor sites,
and the NIH may contact CIAC 24-hours a day. During off hours (5PM -
8AM PST), call the CIAC voice number 925-422-8193 and leave a message,
or call 800-759-7243 (800-SKY-PAGE) to send a Sky Page. CIAC has two
Sky Page PIN numbers, the primary PIN number, 8550070, is for the CIAC
duty person, and the secondary PIN number, 8550074 is for the CIAC
Project Leader.

Previous CIAC notices, anti-virus software, and other information are
available from the CIAC Computer Security Archive.

   World Wide Web:
                        (or -- they're the same machine)
   Anonymous FTP:
                        (or -- they're the same machine)
   Modem access:        +1 (925) 423-4753 (28.8K baud)
                        +1 (925) 423-3331 (28.8K baud)

CIAC has several self-subscribing mailing lists for electronic
1. CIAC-BULLETIN for Advisories, highest priority - time critical
   information and Bulletins, important computer security information;
2. SPI-ANNOUNCE for official news about Security Profile Inspector
   (SPI) software updates, new features, distribution and
3. SPI-NOTES, for discussion of problems and solutions regarding the
   use of SPI products.

Our mailing lists are managed by a public domain software package
called Majordomo, which ignores E-mail header subject lines. To
subscribe (add yourself) to one of our mailing lists, send the
following request as the E-mail message body, substituting
ciac-bulletin, spi-announce OR spi-notes for list-name:

E-mail to or
        subscribe list-name
  e.g., subscribe ciac-bulletin

You will receive an acknowledgment email immediately with a confirmation
that you will need to mail back to the addresses above, as per the
instructions in the email.  This is a partial protection to make sure
you are really the one who asked to be signed up for the list in question.

If you include the word 'help' in the body of an email to the above address,
it will also send back an information file on how to subscribe/unsubscribe,
get past issues of CIAC bulletins via email, etc.

PLEASE NOTE: Many users outside of the DOE, ESnet, and NIH computing
communities receive CIAC bulletins.  If you are not part of these
communities, please contact your agency's response team to report
incidents. Your agency's team will coordinate with CIAC. The Forum of
Incident Response and Security Teams (FIRST) is a world-wide
organization. A list of FIRST member organizations and their
constituencies can be obtained via WWW at

This document was prepared as an account of work sponsored by an
agency of the United States Government. Neither the United States
Government nor the University of California nor any of their
employees, makes any warranty, express or implied, or assumes any
legal liability or responsibility for the accuracy, completeness, or
usefulness of any information, apparatus, product, or process
disclosed, or represents that its use would not infringe privately
owned rights. Reference herein to any specific commercial products,
process, or service by trade name, trademark, manufacturer, or
otherwise, does not necessarily constitute or imply its endorsement,
recommendation or favoring by the United States Government or the
University of California. The views and opinions of authors expressed
herein do not necessarily state or reflect those of the United States
Government or the University of California, and shall not be used for
advertising or product endorsement purposes.

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