=============================================================================== Security Advisory CERT-NL =============================================================================== Author/Source : CERT-NL (Erik-Jan Bos) Index : S-94-21 Distribution : World Page : 1 Classification: External Version: Final Subject : Trojan Horse in IRC Client for UNIX Date : 21-Oct-94 =============================================================================== CERT-NL 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-NL 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 an APPENDIX file with the same index number as this Security Advisory. CERT-NL advisories and their associated APPENDIX files are available by anonymous FTP from ftp.nic.surfnet.nl (see footer of this message). We encourage you to check the APPENDIX 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 | egrep '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 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. --------------------------------------------------------------------------- CERT-NL wishes to thank The CERT Coordination Center for making this information available. ============================================================================== CERT-NL is the Computer Emergency Response Team, located in The Netherlands. CERT-NL is a Full Member of the Forum of Incident Response and Security Teams (FIRST). The constituency of CERT-NL are the SURFnet connected institutions. Past CERT-NL Security Bulletins and other CERT-NL related material can be found on the anonymous FTP server of SURFnet bv: "ftp.nic.surfnet.nl" [192.87.46.3], in the directory "surfnet/net-security/cert-nl/docs/bulletin". This information is also available using email. Send an email saying "help" to "mailserv@nic.surfnet.nl". In case of computer or network security problems please contact CERT-NL or the CERT of your own constituency. Please be aware of the fact that we are one (when DST is in effect two) hour(s) ahead of Universal Time Coordinated (i.e. UTC+0100 (UTC+0200)). Email: cert-nl@surfnet.nl Phone: +31 30 310290 Fax: +31 30 340903 Snailmail: SURFnet bv Attn. CERT-NL P.O. Box 19035 NL - 3501 DA UTRECHT The Netherlands A 7 * 24 hours phone number is available to SURFnet SSC's and FIRST members on request. ==============================================================================