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CA-94:14                         CERT Advisory
                                October 19, 1994
                      Trojan Horse in IRC Client for UNIX
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The CERT Coordination Center has learned of a Trojan horse in some copies of
ircII version 2.2.9, the source code for the Internet Relay Chat (IRC) client
for UNIX systems. Reports we have received thus far indicate that the corrupt
code was available as early as May 1994. The Trojan horse provides a back door
through which intruders can gain unauthorized access to accounts of IRC users.
Intruders are actively exploiting this back door.  If you obtained ircII 2.2.9
from any site in May or later, you may be vulnerable.

Because it is unknown how far the corrupt version of the IRC client has
propagated and because intruders may have corrupted other versions, the CERT
staff recommends obtaining and installing ircII version 2.6. 

Because no special privileges are needed to install and run the IRC source
code, any user on your system may have installed the corrupt code.  Thus, we
also recommend that you inform your users of this potential problem and its
solution.

As we receive additional information relating to this advisory, we will place
it, along with any clarifications, in a CA-94:14.README file. CERT advisories
and their associated README files are available by anonymous FTP from
info.cert.org. We encourage you to check the README files regularly for
updates on advisories that relate to your site.

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I.   Description

     A Trojan horse was found in some copies of the source code for
     the Internet Relay Chat client for UNIX systems, ircII version
     2.2.9.  Intruders are actively exploiting this Trojan horse.

     The Trojan horse creates a back door and enables intruders to
     gain unauthorized access to accounts of IRC users. If IRC is run
     from a system account, such as root or bin, the Trojan horse
     enables intruders to gain unauthorized access to the system
     account.  In addition, because it is possible to compile,
     install, and run IRC source code without special privileges, any
     user on your system may have installed corrupt code.

     The source code containing the Trojan horse was available from
     many FTP sites as early as May 1994 (at this time, we do not have
     a specific date).

II.  Impact

     Remote users can gain unauthorized access to any account running
     the IRC client, including a system account if it is running IRC.

III. Solution

     If you want to try to determine whether your copy of ircII contains the
     Trojan horse, perform a search on the IRC client to find the strings JUPE
     or GROK. For example, 

        % strings /usr/local/bin/irc | grep 'JUPE|GROK'

     If the strings JUPE or GROK are present in the IRC client, your source
     code may contain the Trojan horse. Keep in mind, however, that back doors
     can easily be changed to respond to other words, so you may be vulnerable
     even if you do not find JUPE or GROK.

     Thus, even if you believe that your IRC source code is clean, we urge you
     to install ircII version 2.6, the most recent version of IRC. Also,
     the maintainer of the code reports that version 2.6 contains many bug
     fixes and extra portability. 

     IRC source code is available by anonymous FTP from many locations,
     including the following:

        sungear.mame.mu.oz.au:/pub/irc
        alpha.gnu.ai.mit.edu:/ircII (2.6 not available as of 10/19/94)
        ftp.funet.fi:/pub/unix/irc/ircII
        coombs.anu.edu.au:/pub/irc/ircii

        File                  Size     MD5 Checksum
        --------              ------   -----------------------------
        ircii-2.6.tar.gz      366361   3FC5FBD18CB3E6C071F51FD8C6C59017
        ircii-2.6help.tar.gz  111733   D9D535B7A06BED2A2EA6676B20BDA481
        ircii-2.5to2.6-diff   19644    0C05C96B10CB87186BD921536AE3FDF2
       
IV.  Informing Users

     Because users may have installed IRC source code on their own, we
     recommend informing all your users about the Trojan horse and the new
     version of IRC.

     In addition, you may want to find any user-installed copies of IRC that
     may be vulnerable. If so, you could use the find command to locate these
     binaries. As an example, the following command will enable you to find
     all files named "irc" in a subdirectory of /usr/users:
      
        % find /usr/users -name irc -type f -print

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The CERT Coordination Center wishes to thank Matthew Green for his 
assistance with this advisory.
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If you believe that your system has been compromised, contact the CERT
Coordination Center or your representative in Forum of Incident
Response and Security Teams (FIRST).

If you wish to send sensitive incident or vulnerability information to
CERT via electronic mail, CERT strongly advises that the e-mail be
encrypted.  CERT can support a shared DES key, PGP (public key
available via anonymous FTP on info.cert.org), or PEM (contact CERT
for details).

Internet E-mail: cert@cert.org
Telephone: 412-268-7090 (24-hour hotline)
           CERT personnel answer 8:30 a.m.-5:00 p.m. EST(GMT-5)/EDT(GMT-4),
           and are on call for emergencies during other hours.

CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh, PA 15213-3890
USA

Past advisories, information about FIRST representatives, and other
information related to computer security are available for anonymous
FTP from info.cert.org.

