I have a Windows XP Pro dual booting with Ubuntu Jaunty Jackelope on a single hard drive. On Windows XP I have a Eset NOD 32 while on Ubuntu I have no antivirus installed.

While working on the internet via Ubuntu, if a virus gets into my PC, it might probably not do much damage to Ubuntu as most of these virus' are designed for windows however I'm still worried that they may continue to reside on my Ubuntu partition...

  • and since I am working in dual boot mode ( not sharing any partitions at the moment) will the virus affect the windows partition?
  • Alternatively since I am using a thumb drive to transfer data between Ubuntu and Win XP the virus might propogate through the flash drive?

Can I stop the virus from entering the system via Ubuntu and how?


It's certainly possible to infect Windows through Ubuntu. It can happen if you have an infected file that gets transferred from one OS to the other; however, an infected file that lives only on the Linux partition will probably not have any affect on the Windows OS.

The easiest way to keep Windows clean is to use an antivirus application in Windows. It might be a bit overkill to also install an antivirus app in Ubuntu as well; however, if you want, you could use something like ClamAV to scan files before transferring them to Windows. There's more info on ClamAV in this question on SuperUser.

The good thing about ClamAV is that it's an on-demand scanner, so it doesn't consume any resources when you don't need it. That way, when you transfer files from Ubuntu to Windows, all you need to do is scan them before copying them over to the other OS.

  • Hmm! the system is working in this mode currently but I have other pc's (Windows) networked to mine and I don't want to risk getting a virus on my Ubuntu partition.. so what can I do to bar the virus? – Kevin Boyd Oct 6 '09 at 6:51
  • Well, currently what I do is restart each time I want to cross over to another system (Ubuntu or Windows)... so do I need to expose some part of the partion to trasnfer files on to the other... how do I do that ? – Kevin Boyd Oct 6 '09 at 7:10
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    Well, I have a similar setup as you. I dual boot Windows and Mac OS X, but I haven't really bothered much with viruses. Both Mac OS and Linux can read and write NTFS partitions with a bit of work (in Mac OS you need ntfs3g and MacFuse, in Linux I think ntfs3g is enough). I have no antivirus on Mac OS X, but I use one in Windows (I use Microsoft Security Essentials). This setup is really more than enough; there's no need to worry that much. – alex Oct 6 '09 at 7:17
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    Instead of ClamAV, one can use AVG Linu which was free when I used it 6 months ago. It is too on demnad so no waste of resource. – Ganesh R. Oct 6 '09 at 9:17

In theory, yes there is a risk. In the real world - almost no chance.

Keep in mind that malware needs to be executed before it can do any damage. If you have malware.exe, simply having it does nothing, the file needs to be executed. If it's opening a compromised picture file, or running an exe, the code inside the nasty file needs to be executed.

Even if you have WINE or some other emulation system on your machine, chances are pretty good it won't do any harm to your Windows partition, because most malware just simply isn't looking for another partiton.

Malware and other nasties are designed to target the widest array of users, to ensure maximum penetration for little effort. I'd be willing to bet that most malware in the wild will be unable to affect your Windows partition, unless it's specifically designed to do so.

  • Isn't it possible that it just targets my Thumb drive went I am copying something from Ubuntu...then in stays there and transfers itself to windows on another transfer operation.. – Kevin Boyd Oct 6 '09 at 7:12
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    Yes, that's possible - but the malware would need to be specifically designed to run under a WINE environment, target your thumbdrive and then run again in Windows. It's possible, but I'd say that your chances of winning powerball are more likely than coming across such a specific piece of malware as that. – EvilChookie Oct 6 '09 at 7:16

It's certainly possible, although far-fetched:
If the Linux malware has read-write access to the Windows partition, it can then modify any Windows file that it likes, and that way infect the other partition.

The malware needs to be designed as cross-system, but with the sophisticated multi-vector attacks that we're seeing today, everything is possible.

The only protection would be to ensure that Ubuntu doesn't have write access to the Windows partition.

  • and how do I ensure that Ubuntu doesn't have write access to the Windows partition? – Kevin Boyd Oct 6 '09 at 8:36
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    by defining the right access rights to the Windows partition through the fstab file. Ideally, only root should have any kind of access. – harrymc Oct 6 '09 at 9:15
  • harrymc: I thought Ubuntu was the operating system as a whole, including the kernel, which of course can do anything it likes... – SamB Dec 10 '10 at 23:19
  • @SamB: Each protection by itself can be countered by the virus. To avoid all possible protections, a virus needs to be of military grade. – harrymc Dec 11 '10 at 6:12
  • @harrymc Can you prevent only Windows system files from being written to? Or maybe have "shared" folders (between Windows and Ubuntu) on the Windows partition? – Mateen Ulhaq May 23 '11 at 8:19

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