CERT® Advisory CA-1994-14 Trojan Horse in IRC Client for UNIXOriginal issue date: October 19, 1994
Last revised: September 23, 1997
Updated copyright statement
A complete revision history is at the end of this file.
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.
We will update this advisory as we receive additional information. Please check advisory files regularly for updates that relate to your site.
I. DescriptionA 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. ImpactRemote users can gain unauthorized access to any account running the IRC client, including a system account if it is running IRC.
III. SolutionIf 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' % 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:
File Size MD5 ChecksumAs of Feb. 2, 1995, an ircii2.6-sco-patch is available:
File Size MD5 Checksum
IV. Informing UsersBecause 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.
This document is available from: http://www.cert.org/advisories/CA-1994-14.html
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Conditions for use, disclaimers, and sponsorship information
Copyright 1994, 1996 Carnegie Mellon University.
Sep. 23, 1997 Updated copyright statement Aug. 30, 1996 Information previously in the README was inserted into the advisory. Feb. 02, 1995 Sec. III - Added filenames and checksums for ircii2.6-sco-patch. Oct. 20, 1994 Sec. III - Added example command using egrep. Included alhpa.gnu.ai.mit.edu as a source of ircII.