Registered: Jul 2000
Location: Beatrice, Nebraska
Posts: 18928

http://articles.linuxguru.net/view/198

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The WINE project is becoming increasingly popular and useful to those who would continue to use proprietary, free, and unported opensource software available only for Microsoft Windows. I've tested it with a few games I had purchased while I still used Windows, and it surprised me. The WINE project, and the two popular forks in the project, WineX, and Codeweavers WINE, have come along quite nicely, albeit it slowly, over the last few years. I give a lot of credit to the many developers that have poured a lot of their time into the project, but, with the good, the bad must be accepted.

Recently a friend of mine, proficient in Linux, and not what you would call a 'newbie' to computing, received an email from a customer. The email was vague and included an attachment. In KMail, he decided to view the attachment, thinking it was simply an image. He clicks it, nothing happens, no viewer, no error, nothing but a few seconds of milling around, and then more nothing. Then, the wine notification pops up. By this time he had realized the file was a Windows executable, and that he'd just executed it with wine because of the MIME typing capabilities of KDE, and WINE's integration with the desktop.

If he were running windows, I would've slapped him upside the head, everyone with any sense at all would've expected an odd email with an attachment to be a ready and willing virus or worm. Of course, this was no different, this attachment contained the worm known as WORM_KLEZ.H. However, because of the sense of security from worms of this nature bestowed to Linux users, by the same type of ignorance in assumption that spreads them amongst Windows users, he never expected the attachment to be a virus or worm that would infect and operate as it normally does. Unfortunately, this is exactly what happened... click, boom, Klez goes nuts, etc., etc., etc.

The virus itself is simply a worm, it's what you'd call a 'dumb virus', in the sense that it isn't extremely complex, doesn't change itself around much, and basically works as fast as it can before it is easily obliterated by common virus scanning software. The basic idea is that it infects you, spreads itself by emailing from your computer to as many contacts as possible, then does its damage, if you want more detailed information, Trend Micro has plentiful information about Klez and other viruses and worms available on http://www.antivirus.com/.

Now, you may be wondering how it infected and actually 'worked', I know I certainly was. In this particular case, our cool customer known from here on out as 'John' for 'John Doe', had wine installed, and you see, the default configuration for most wine installs, shares your root linux directory as a drive visible to the applications running inside of it. If you know anything about the Klez worm, you'll remember that not only does it search for address books, etc, it will search for many other common file formats on the entire system, searching for email addresses, dropping PE_ELKERN.D, and various other silly virus/worm/intrusive type things.

So far we have the first two parts of the Klez's basic operation, infection, and email address reaping. What is next? Let's say it together kids "PROP A GA TION" yay!!! Now, this is probably one of the most important parts of a worm's life cycle. If it doesn't propagate, it isn't really a worm or a virus. It's just a pointless, irritating program.

Propagation in wine, this was the part in this particular case that I found so amusing. The computer was running a secure MTA (Mail Transport Agent) and the fake Windows registry for WINE was configured to use the localhost as the SMTP server for internet applications. Otherwise, the Klez would not have known how to send itself. It is possible, that, the Klez worm defaults to 'localhost' for the SMTP server if it cannot find one in the registry, this I don't know and it doesn't seem to be covered in Trend Micro's technical description. Anyway, because of the MTA being localhost, the worm was able to queue all of its outgoing email quite quickly. I actually had the opportunity to remotely shell in as root and view `ps aux` output, showing the various smtpd instances sending this email, while I tried to help John find the spooled emails and remove them.

Now, a few things must be noted about this particular situation. KLEZ is not a high risk worm, so by no means was this a massive problem for this person. Also, the infection did not include files that were not Windows exectuables, so the native filesystem was left unharmed. The spooled emails were taken care of and the effects overall were minimal, if not simply classified as an 'annoyance.'

The reason this is such an important subject to cover, isn't this instance of infection, but, the possible vulnerability that using WINE in such an insecure (and default) way can provide. For example, a knowledgeable virus programmer could use this situation to make multi-platform viruses, that could detect files by their 'magic file type' similar to the way the tool 'file' does, and infect them through wine. I understand, that this is highly unlikely to occur any time soon, but, I think you can probably imagine many other ways that this opens doors for virus problems to the relatively virus-clean environment of Linux.

The main points I'd like to make are: WINE is obviously mature enough to handle the more advanced code that a virus usually contains. Even if only KLEZ for now, others will in the future, be compatible. The other is: I am willing to bet that 90% of you WINE users out there, can view drive Z, or something similar and get your root file system tree, and something like drive Y provides your home directory READ-WRITE. Please, don't do this, unless it is absolutely necessary, minimize the interaction between your WINE environment, and the real linux environment, specify a directory for wine shared files and keep them separate from your linux home files, etc. This will help to minimize the post-infection damage a virus can accomplish.

Finally, the most important 'bug' most distributions have, is allowing a Windows executable to be run with wine without an obvious chance for interception, by default. Sure, it comes up with a window, telling you that wine is running, and allowing you to disable the notice, however, it does NOT warn you about the application being executed in such a way that you could stop it before it was started. Even Java does this with code that is signed for permissions; it still asks you if you are sure you want to give it permissions.

As it goes, I was unable to easily obtain any previously written information on securing WINE properly, and I am no security expert. Some basic tips would include, configuring the program, read all of the options, don't let it set itself up completely for you.If anyone has any tips they would like to share, please do.

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