Archive of CERT general posting, CERT Advisory CA-2001-19

20/07/01, CERT Advisory CA-2001-19
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Subject: CERT Advisory CA-2001-19
From: CERT Advisory <>
Date: Thu, 19 Jul 2001 19:14:52 -0400 (EDT)
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Organization: CERT(R) Coordination Center - +1 412-268-7090


CERT Advisory CA-2001-19 "Code Red" Worm Exploiting Buffer Overflow In IIS
Indexing Service DLL

   Original release date: July 19, 2001
   Source: CERT/CC

   A complete revision history can be found at the end of this file.

Systems Affected

   Systems running Microsoft Windows NT 4.0 and Windows 2000 with IIS 4.0
   or IIS 5.0 enabled


   The CERT/CC has received reports of new self-propagating malicious
   code that exploits certain configurations of Microsoft Windows
   susceptible to the vulnerability described in CERT advisory CA-2001-13
   Buffer Overflow In IIS Indexing Service DLL. These reports indicate
   that the "Code Red" worm may have already affected as many as 225,000
   hosts, and continues to spread rapidly.


   In examples we have seen, the "Code Red" worm attack proceeds as
     * The victim host is scanned for TCP port 80 by the "Code Red" worm.
     * The attacking host sends a crafted HTTP GET request to the victim,
       attempting to exploit a buffer overflow in the Indexing Service
       described in CERT advisory CA-2001-13
     * If the exploit is successful, the worm begins executing on the
       victim host. Initially, the existence of the c:\notworm file is
       checked. Should this file be found, the worm ceases execution.
     * If c:\notworm is not found, the worm begins spawning threads to
       scan seemingly random IP addresses for hosts listening on TCP port
       80, exploiting any vulnerable hosts it finds.
     * If the victim host's default language is English, then after 100
       scanning threads have started and a certain period of time has
       elapsed following infection, all web pages served by the victim
       host are defaced with the message

         HELLO! Welcome to! Hacked By Chinese!

     * If the victim host's default language is not English, the worm
       will continue scanning but no defacement will occur.

System Footprint

   The "Code Red" worm can be identified on victim machines by the
   presence of the following string in IIS log files:


   Additionally, web pages on victim machines may be defaced with the
   following message:

     HELLO! Welcome to! Hacked By Chinese!

   The text of this page is stored exclusively in memory and is not
   written to disk. Therefore, searching for the text of this page in the
   file system may not detect compromise.

Network Footprint

   A host running an active instance of the "Code Red" worm scans random
   IP addresses on port 80/TCP looking for other hosts to infect.

   Additional detailed analysis of this worm has been published by eEye
   Digital Security at


   In addition to web site defacement, infected systems may experience
   performance degradation as a result of the scanning activity of this

   Non-compromised systems and networks that are being scanned by other
   hosts infected by the "Code Red" worm may experience severe denial of
   service. This occurs because each instance of the "Code Red" worm uses
   the same random number generator seed to create the list of IP
   addresses it scans. Therefore, all victim hosts scan the same IP

   Furthermore, it is important to note that while the "Code Red" worm
   appears to merely deface web pages on affected systems and attack
   other systems, the IIS indexing vulnerability it exploits can be used
   to execute arbitrary code in the Local System security context. This
   level of privilege effectively gives an attacker complete control of
   the victim system.


   The CERT/CC encourages all Internet sites to review CERT advisory
   CA-2001-13 and ensure workarounds or patches have been applied on all
   affected hosts on your network.

   If you believe a host under your control has been compromised, you may
   wish to refer to


   The CERT/CC is interested in receiving reports of this activity. If
   machines under your administrative control are compromised, please
   send mail to with the following text included in the
   subject line: "[CERT#36881]".

   Author(s): Roman Danyliw and Allen Householder

   This document is available from:

CERT/CC Contact Information

          Phone: +1 412-268-7090 (24-hour hotline)
          Fax: +1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890

   CERT personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4)
   Monday through Friday; they are on call for emergencies during other
   hours, on U.S. holidays, and on weekends.

Using encryption

   We strongly urge you to encrypt sensitive information sent by email.
   Our public PGP key is available from

   If you prefer to use DES, please call the CERT hotline for more

Getting security information

   CERT publications and other security information are available from
   our web site

   To subscribe to the CERT mailing list for advisories and bulletins,
   send email to Please include in the body of your

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   * "CERT" and "CERT Coordination Center" are registered in the U.S.
   Patent and Trademark Office.

   Any material furnished by Carnegie Mellon University and the Software
   Engineering Institute is furnished on an "as is" basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed or
   implied as to any matter including, but not limited to, warranty of
   fitness for a particular purpose or merchantability, exclusivity or
   results obtained from use of the material. Carnegie Mellon University
   does not make any warranty of any kind with respect to freedom from
   patent, trademark, or copyright infringement.

   Conditions for use, disclaimers, and sponsorship information

   Copyright 2001 Carnegie Mellon University.

   Revision History
Jul 19, 2001: Initial release

Version: PGPfreeware 5.0i for non-commercial use
Charset: noconv


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