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Hacking Linux BIND servers becomes child's play
New worm swipes passwords, installs rootkit
A worm called Lion has been developed to enable any fool to exploit a buffer overflow vulnerability in BIND 8 transaction signature (TSIG) handling code which we reported back in January.
Lion is spread via an application called randb which scans random class B networks probing TCP port 53. Once it hits, it checks to see if the system is vulnerable, and if so exploits it and then installs the t0rn rootkit, according to a SANS Institute advisory issued Friday.
According to SANS, once on a system, it sends the contents of /etc/passwd, /etc/shadow, and some network settings to an address in the china.com domain. It deletes /etc/hosts.deny, lowering some of the built-in protection afforded by tcp wrappers.
Ports 60008/tcp and 33567/tcp get a backdoor root shell, and a Trojanized version of ssh gets placed on 33568/tcp. Syslogd is killed, so the logging on the system can't be trusted, the SANS advisory notes.
A Trojanized version of login is installed. It looks for a hashed password in /etc/ttyhash. Also, /usr/sbin/nscd (the optional Name Service Caching daemon) is overwritten with a Trojanized version of ssh. The t0rn rootkit replaces several binaries on the system in order to hide itself, SANS says.
SANS has posted a file to detect Lion, and of course urges admins to upgrade BIND to patched versions which are no longer vulnerable, after confirming that their systems are clean.
No information is yet available from SANS on where or even if the worm has been used in the wild. However, the FBI's National Infrastructure Protection Center (NIPC) claims that Lion attackers are "infecting computers and installing distributed denial of service tools on various computer systems."
The NIPC claims that Lion also installs the Tribe Flood Network (tfn2k) DDoS client, though, oddly, the SANS advisory makes no mention of this alarming detail.
"Illegal activity of this nature typically is designed to create large networks of hosts capable of launching coordinated packet flooding denial of service attacks. Possible motives for this malicious activity include exploit demonstration, exploration and reconnaissance, or preparation for widespread denial of service attacks," the NIPC warns ominously.
OK, we get it. Digital catastrophe is just around the corner and that's why you guys need to keep monitoring ISPs with Carnivore. ®