TCPDump / LIBPCap Trojan Horse Vulnerability



Date Discovered

November 13, 2002


It has been announced that the server hosting tcpdump and libpcap,, was compromised recently. It has been reported that the intruder made modifications to the source code of tcpdump and libpcap to include trojan horse code. Downloads of the source code of tcpdump and libpcap from, and numerous mirrors, likely contain the trojan code. Reports say that the trojan will run once upon compilation of tcpdump or libpcap. Once the trojan is executed, it attempts to connect to host on port 1963. The MD5 sums of the trojaned versions are reported to be: MD5 Sum 73ba7af963aff7c9e23fa1308a793dca libpcap-0.7.1.tar.gz MD5 Sum 3a1c2dd3471486f9c7df87029bf2f1e9 tcpdump-3.6.2.tar.gz MD5 Sum 3c410d8434e63fb3931fe77328e4dd88 tcpdump-3.7.1.tar.gz The MD5 sums of the non-trojaned versions are: MD5 Sum 0597c23e3496a5c108097b2a0f1bd0c7 libpcap-0.7.1.tar.gz MD5 Sum 6bc8da35f9eed4e675bfdf04ce312248 tcpdump-3.6.2.tar.gz MD5 Sum 03e5eac68c65b7e6ce8da03b0b0b225e tcpdump-3.7.1.tar.gz The non-trojaned versions of these tools are available at the following locations: Additionally, the trojan displays similarity to those found in irssi, fragroute, fragrouter, BitchX, OpenSSH, and Sendmail.

Technologies Affected

  • LBL libpcap 0.5.0
  • LBL libpcap 0.7.0
  • LBL libpcap 0.7.1
  • LBL tcpdump 3.4.0
  • LBL tcpdump 3.5.0
  • LBL tcpdump 3.6.2
  • LBL tcpdump 3.7.0
  • LBL tcpdump 3.7.1


Block external access at the network boundary, unless external parties require service.
Filter untrusted network traffic at border routers and network firewalls.

Run all software as a nonprivileged user with minimal access rights.
Perform all tasks with the minimal privileges possible.

It has been recommended that users that require tcpdump or libpcap use either a known, good version of tcpdump 3.62, tcpdump 3.71 or libpcap 0.71.



Discovery of this vulnerability credited to Russell Adams <>, Mathew Solnik <>, and Scott Stout <>.

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