============================================================================= CA-94:14 CERT Advisory October 19, 1994 Trojan Horse in IRC Client for UNIX ----------------------------------------------------------------------------- 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. ----------------------------------------------------------------------------- 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 --------------------------------------------------------------------------- The CERT Coordination Center wishes to thank Matthew Green for his assistance with this advisory. --------------------------------------------------------------------------- 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.