Over the last few days, a new worm, Linux.Plupii, which attacks Linux systems via Web-server related services, has made its appearance.
This worm, also known as Linux/Lupper.worm or luppi, is a blended threat. It attempts to use three different Web-service security holes in its attempts to infect Linux-based systems that are running the vulnerable services.
The three vulnerabilities it attacks through are the XML-RPC for PHP Remote Code Injection vulnerability; the AWStats Rawlog Plugin Logfile Parameter Input Validation Vulnerability; and the Darryl Burgdorf Webhints Remote Command Execution Vulnerability.
The XML-RPC hole commonly exists in blogging and Wiki programs. There are now fixes available for this hole for most systems.
AWStats is a popular, open-source log-file analyzer. Only servers which run AWStats 5.0 to 6.3 can be attacked. Versions 6.4, which came out in March, and higher are immune.
Finally, Webhints is an older script program that's designed to set up and maintain a "Hint (Quote/Tip/Joke/Whatever) of the Day" page. Version 1.3 is vulnerable to attack. There is, at this time, no known fix for the program.
When Plupii is successful in infecting a server, it then sends a notification message to an attacker at a remote IP address via UDP port 7222 or 7111. Which port it attacks appears to be hard-wired into the worm and thus represents two different versions of the same worm. Next, it opens a back door through one or the other of these ports. This enables an attacker to gain unauthorized access to the compromised system.
Once in place, Plupii generates a variety of URLs. It uses these, via the default Web server port, 80, in an attempt to find and infect other vulnerable systems.
The worm itself is easy to destroy. One need only delete the file: /tmp/lupii. The more significant problem is what the attacker may have downloaded to the server while it was active.
Indeed, Symantec's Deepsight Alert Services recommends that, "Due to the ability of the remote user to perform so many different actions on the server computer, including installation of applications, it is highly recommended that compromised computers be completely reinstalled."
Symantec also reported that many major Linux distributions, including Red Hat, SUSE and Turbolinux, can be impacted by this worm. Given that the list includes most major Linux 2.4 and 2.6 distributions, it can be presumed that any Linux running an application that employs one of the vulnerable programs may be at risk.
According to the Internet Storm Center, this worm is operating in the wild on the Internet.
All the major anti-virus vendors, including Symantec Corp., McAfee Inc., and Computer Associates International Inc. and open source anti-viral programs like ClamAV now have signature files for the worm.
The worm can also be stopped in the first place by avoiding all use of Webhints and using only patched versions of AWStats and PHP.