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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 [email protected] 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

Email: [email protected]
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 [email protected]. Please include in the body of your

subscribe cert-advisory

* "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

111 Posts
Hey - anyone who is crazy enough to run IIS and think it's secure will know this is just one of many many holes:eek: :eek:
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