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May 28, 1998

This special edition of the CERT Summary reports new types of exploit methods
related to those discussed in CS-98.04. Special Edition CERT Summary CS-98.04
is available at

All of these attacks occur on machines running "named" (domain name server
software, part of BIND).

Past CERT Summaries are available from
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The CERT Coordination Center has received reports of new kinds of intruder
activity indicating that intruders are targeting machines running vulnerable
versions of "named" (domain name server software that is part of
BIND). Thousands of sites running unpatched, vulnerable versions of "named"
are known to have been compromised through exploit methods discussed here and
in CS-98.04.

Most of the compromised machines reported to us have been Intel-based machines
running Linux; however, machines of other architectures running vulnerable
versions of "named" have had their "named" processes crash.

While intruders appear to be using tools that exploit this vulnerability on
Intel-based machines, it would not be difficult for intruders to adapt
existing tools to exploit the vulnerability on other architectures.

We encourage you to review CERT Advisory CA-98.05, which describes the BIND
inverse query vulnerability that is being exploited, and to apply the
appropriate patches if you have not done so already. The advisory is available

Since the creation of the CERT/CC nearly 10 years ago, part of our mission has
been and is to facilitate communications between affected sites and law
enforcement agencies. The CERT/CC has been informed by the FBI (Federal Bureau
of Investigation) that they are actively investigating compromises related to
this special edition CERT summary. The FBI is seeking information from
affected sites on the exploitation of these vulnerabilities. If you would like
to report activities at your site to the FBI, please contact the FBI at

	phone:	+1 202 324 6715
	email:	This email address is being protected from spambots. You need JavaScript enabled to view it.

or the CERT/CC.

Description of New Attack Methods
- ---------------------------------
In addition to the current attacks described in CS-98.04, other toolkits have
been discovered, including one with the potential to be self-replicating. The
self-replicating tool does not replicate by default.

Sites that have applied patches or upgraded to a version of "named" that is
not vulnerable to the inverse query vulnerability (described in CA-98.05) are
not vulnerable to this attack method.

Currently, this toolkit attempts to compromise a machine using the bind
inverse query vulnerability. If the exploitation attempt is successful, it can

     -  Create a blank line in the password file and add the user
        "w0rm" to the password file (with no password)

     -  Create a root setuid version of the shell (/bin/sh)
        in /tmp/.w0rm 

     -  Remove the file /etc/hosts.deny 

     -  Restart "named" (because the exploit of the buffer overflow
        will cause "named" to crash)

     -  Create the file /tmp/.X11x with an html page. The toolkit
        also attempts to look for index.html files located on the
        file system of the compromised machine and attempts to 
        alter them. This attempt fails in the toolkit as it is 
        currently distributed.

     -  Create the directory /tmp/.w0rm0r and the file /tmp/w0rmishere

     -  Get the tar file called ADMw0rm.tgz via ftp from the
        previously compromised machine, unpack it, and place it in

     -  Execute the ADMw0rm command from the downloaded archive

     -  Send via email the IP address of the local machine to
        an external email address

     -  Remove any logs located in /var/log/* and the file /tmp/.w0rm

The order in which these steps are performed might vary, and all steps might
not be performed in all compromises.

In other attack methods, we are seeing intruders compromise machines running
vulnerable versions of "named"; as part of the exploit they open xterm windows
from the compromised machine, displaying back to the intruder's machine. The
intruder then has a privileged interactive session on the compromised machine.

What to Look for
- ----------------
In addition to the items listed in CERT Summary CS-98.04, you should look for
the following to help you detect this specific activity:

      - Accounts and blank lines added to the password file

      - Logins to unauthorized accounts (accounts created by the

      - The deletion of log files or the hosts.deny file

      - Crashes or restarts of "named"

      - The existence of the files or directories:

      - Unauthorized replacement of index.html files

      - xterm connections originating from internal machines
        displaying on remote machines

If you determine that your systems might have been root compromised as a
result of this activity, we recommend that you disconnect the affected host
from the network and encourage you to refer to the "Recovering from an
Incident" web page available at

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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 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

To be added to our mailing list for CERT advisories and bulletins, send your
email address to 
        This email address is being protected from spambots. You need JavaScript enabled to view it.
In the subject line, type
        SUBSCRIBE your-email-address

CERT advisories and bulletins are posted on the USENET news group

CERT publications, information about FIRST representatives, and other
security-related information are available for anonymous FTP from

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

Location of CERT PGP key

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Copyright 1998 Carnegie Mellon University. Conditions for use, disclaimers,
and sponsorship information can be found in and .
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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