Linux

Bootable Thumb Drive Virus Scanner Saves the Day

Forgive me if I brag a bit in this post, but I think I earned the right. You be the judge.

Last weekend, I noticed strange behavior on my home system. ESET Smart Security kept reporting that it had “found and quarantined m.exe, probably a variant of Win.Qhost trojan.” Every time I plugged in a USB thumb drive, ESET would pop up with the message. I couldn’t run HijackThis. If I tried to go to certain antivirus websites–Avira in particular–my browser closed. Sysinternals Process Explorer wouldn’t run. My thumb drive showed two hidden files: Autorun.inf and m.exe. Hmmm. Running ipconfig /displaydns revealed multiple connections to porn and malware sites. Searching Google led me to some tools that eventually fixed my problem at home. Turns out I had a bigger problem.

Apparently, I had picked up the infection from a client’s Exchange server and during my weekly tour there, I found that the tools I used on my XP machine wouldn’t run on Windows Server 2003.  I tried everything in my arsenal; no tool found anything wrong. This thing was very stealthy; even Safe Mode didn’t disable it. I was about to give up. Then I remembered that I’d recently finished making up a bootable Linux thumb drive virus scanner using the AntiVir rescue CD, a tool that allows offline scanning (thank you, Avira, you made it a little easier for me). I booted the server to the thumb drive, ran the scan, rebooted the server, and voila! The infection was gone.

There’s a whole backstory to this incident that I won’t bore you with. Suffice it to say that I’m glad I put in the hours of hacking and research to come up with a really useful tool that I was able to use to help a client. Veni! Vidi! Vici!

CERT Says Linux is Under Attack

It had to happen sooner or later; as Linux gains an ever-increasing foothold (Linux market share to reach 7% in 2008 ) in the market, it will become a viable target for criminal hackers. According to the U.S. Computer Emergency Readiness Team (CERT) in US-CERT Current Activity, attacks are already underway:

US-CERT is aware of active attacks against linux-based computing infrastructures using compromised SSH keys. The attack appears to initially use stolen SSH keys to gain access to a system, and then uses local kernel exploits to gain root access. Once root access has been obtained, a rootkit known as “phalanx2″ is installed.

Phalanx2 appears to be a derivative of an older rootkit named “phalanx”. Phalanx2 and the support scripts within the rootkit, are configured to systematically steal SSH keys from the compromised system. These SSH keys are sent to the attackers, who then use them to try to compromise other sites and other systems of interest at the attacked site.

For now, the attack is easily detected (though variants of the rootkit will likely change its behavior): The attack creates a directory “/etc/khubd.p2/” that is hidden from “ls,” but it can be entered with “cd /etc/khubd.p2″. Any directory named “khubd.p2,” regardless of its location, is hidden from “ls” but can be entered using “cd.” Additionally, “/dev/shm/” may contain files from the attack, so anything unusual in there is suspect. You can also try searching for hidden processes and checking the reference count in “/etc” against the number of directories shown by “ls”.

Check out the full article, “SSH Key-based Attacks” for complete details on risk mitigation and compromise response.

Two Ways to Operate Securely on the Web

If you’ve done any coding at all, you probably have a good idea why software developers often run their untested code in a protected environment–a sandbox. If the software misbehaves, all you have to do is shut down the sandbox and everything returns to normal, no harm done.

A sandbox is also a great way to prevent viruses and other malware from infecting your machine while browsing the web. Confine your browser to its own little box and if any malicious software tries to run, it can’t get to your system, it stays within in the box’s boundaries. Kill the box and you kill the malware. The top, free sandbox program for Windows–the one I use for secure surfing and testing– is Sandboxie. It runs only on Windows and is Vista-compatible. Run Internet Explorer, Firefox, or any other program under Sandboxie and you should be safe.

Flash Update: Seems CheckPoint agrees and has released a product of its own. Check out this article from Dark Reading.

You can also operate securely from inside a virtual machine. This is different from a sandbox in that you actually run an entire operating system, rather than a single program. Many people, this Geek included, use virtual machines to run alternative operating systems like Linux. In a virtual machine, you can do everything you do on a real machine and like the sandbox, if things go wrong, your computer won’t be harmed. A big advantage of the virtual machine over a sandbox is that you can examine the actual behavior of malware and any damage to the OS. Microsoft provides the free Virtual PC and VMware provides its free VMware Player and VMware Server. For the Mac, there’s Parallels (not free). You might want to check out the secure browsing applicance provided for VMware Player.

Security Maxim #9:

When surfing the web, testing unknown programs, or engaging in other activities with the potential to harm your computer, use a sandbox or virtual machine to protect your base system from harm.