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CA-2002-30 Trojan Horse tcpdump and libpcap Distributions
issue date: November 13, 2002
Last revised: --
revision history is at the end of this file.
has received reports that several of the released source
code distributions of the libpcap and tcpdump packages were modified
by an intruder and contain a Trojan horse.
encourage sites that use, redistribute, or mirror the
libpcap or tcpdump packages to immediately verify the integrity of
has received reports that some copies of the source code
for libpcap, a packet acquisition library, and tcpdump, a network
sniffer, have been modified by an intruder and contain a Trojan horse.
distributions were modified to include the malicious
md5sum 3c410d8434e63fb3931fe77328e4dd88 tcpdump-3.7.1.tar.gz
modified distributions began to appear in downloads from the
HTTP server www.tcpdump.org on or around Nov 11 2002 10:14:00 GMT. The
tcpdump development team disabled download of the distributions
containing the Trojan horse on Nov 13 2002 15:05:19 GMT. However, the
availability of these distributions from mirror sites is unknown. At
this time, it does not appear that related projects such as WinPcap
and WinDump contain this Trojan horse.
horse version of the tcpdump source code distribution
contains malicious code that is run when the software is compiled.
This code, executed from the tcpdump configure script, will attempt
connect (via wget, lynx, or fetch) to port 80/tcp on a fixed hostname
in order to download a shell script named services. In turn, this
downloaded shell script is executed to generate a C file (conftes.c),
which is subsequently compiled and run.
conftes.c makes an outbound connection to a fixed IP
address (corresponding to the fixed hostname used in the configure
script) on port 1963/tcp and reads a single byte. Three possible
values for this downloaded byte are checked, each causing conftes.c
respond in different ways:
will cause the Trojan horse to exit
will cause the Trojan to fork itself, spawn a shell, and
redirect this shell to the connected IP address (Note that
communication to and from this shell is obfuscated by XORing all
bytes with the constant 0x89.)
will cause the Trojan horse to close the connection and sleep
for 3600 seconds
the activity of this Trojan horse in tcpdump, libpcap, the
underlying packet-capture library of tcpdump, has been modified
(gencode.c) to explicitly ignore all traffic on port 1963 (i.e., a BPF
expression of "not port 1963").
operating from (or able to impersonate) the remote address
specified in the malicious code could gain unauthorized remote access
to any host that compiled a version of tcpdump with this Trojan horse.
The privilege level under which this malicious code would be executed
would be that of the user who compiled the source code.
sites using libpcap and tcpdump to verify the
authenticity of their distribution, regardless of where it was
to get libpcap and tcpdump
the compromise of these distributions is being investigated, the
tcpdump and libpcap maintainers recommend using the following
that mirror the source code are encouraged to verify the
integrity of their sources. We also encourage users to inspect any and
all other software that may have been downloaded from the compromised
site. Note that it is not sufficient to rely on the timestamps or
sizes of the file when trying to determine whether or not you have a
copy of the Trojan horse version.
hashes of the vendor suggested updates for libpcap and tcpdump
are as follows:
As a matter
of good security practice, the CERT/CC encourages users to
verify, whenever possible, the integrity of downloaded software. For
more information, see
A. - Vendor Information
contains information provided by vendors for this
advisory. As vendors report new information to the CERT/CC, we will
update this section and note the changes in our revision history. If
particular vendor is not listed below, we have not received their
checked all our released libpcap and tcpdump packages and
confirmed that they do not contain the trojan code.
packages are only distributed in Debian/unstable. I
have examined both source packages and they did not contain the
trojan code the HLUG reported on their web page. Hence, I guess
that Debian distributes safe source.
examined our sources, and our software does not contain
this trojan. We are not vulnerable to this advisory.
products are not vulnerable.
can be directed to the author: Roman Danyliw, Chad Dougherty.
is available from:
Phone: +1 412-268-7090 (24-hour hotline)
Fax: +1 412-268-6989
CERT Coordination Center
Software Engineering Institute
Carnegie Mellon University
Pittsburgh PA 15213-3890
personnel answer the hotline 08:00-17:00 EST(GMT-5) /
EDT(GMT-4) Monday through Friday; they are on call for emergencies
during other hours, on U.S. holidays, and on weekends.
urge you to encrypt sensitive information sent by email.
Our public PGP key is available from
prefer to use DES, please call the CERT hotline for more
and other security information are available from
our web site
to the CERT mailing list for advisories and bulletins,
send email to email@example.com. Please include in the body of your
and "CERT Coordination Center" are registered in the U.S.
Patent and Trademark Office.
Any material furnished by Carnegie Mellon University and the Software
Engineering Institute is furnished on an "as is" basis. Carnegie
Mellon University makes no warranties of any kind, either expressed
implied as to any matter including, but not limited to, warranty of
fitness for a particular purpose or merchantability, exclusivity or
results obtained from use of the material. Carnegie Mellon University
does not make any warranty of any kind with respect to freedom from
patent, trademark, or copyright infringement.
for use, disclaimers, and sponsorship information
2002 Carnegie Mellon University.
November 13, 2002: Initial release
Version: PGP 6.5.8
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