How to use Linux to save a Windows PC from a virus

If you use Linux on your company's desktop or server computers, you're already familiar with many of the security advantages the open source operating system offers over its Windows and Mac rivals. What many people don't realise, however, is that Linux can also be used to rescue a computer that has been crippled by malware.

Malware is a frequent occurrence in the Windows world in particular, and it can be devastating. When a Windows virus strikes, not only can it become difficult or even impossible to continue using the affected machine, but it can be dangerous as well, since prolonged use can further the infection.

That's where Linux can be a life-saver. Without ever having to install the free alternative, you can still use it temporarily on a PC to get rid of any infection. Here's how.

1. Get a LiveCD or Live USB

LiveCDs and USBs are a wonderful thing in the Linux world because they let you boot a machine directly from the CD or USB stick without ever having to access the computer's boot records. Not only are they a great way to take Linux for a test-drive, but they can also be put to work when Windows can't.

By far the fastest way to get a LiveCD or USB is to download the .iso file of the Linux distribution you'd like to use and then burn it onto a CD or USB stick. Since Ubuntu is the most popular distribution out there, I'll go with Maverick Meerkat, the latest version of the software, for this example.

Ubuntu can be downloaded from the project's website for use on a LiveCD or USB, download links for other distributions can be found listed on FrozenTech. UNetbootin is another nice option if you want to go the USB route, which tends to run much faster.

Of course, to take either of these options you'll have to have a working, Internet-connected computer. If you don't, or if your Internet connection is slow, you may want to order a LiveCD or USB via snail mail. OSDisc and LinuxCD both offer a variety of options.

2. Boot into Linux

Once you're equipped with a Linux LiveCD or USB, you'll need to make sure the infected computer is turned off, and then turn it on again with the CD or USB installed. This will boot the computer into Linux, completely bypassing Windows and its infection. Again, nothing has been installed, you're simply using Linux to get the machine running reliably again.

3. Get antivirus software

Next it's time to get the Linux-based ammunition you'll need to wipe out the malware: antivirus software. I'm going to use my favourite ClamAV, via ClamTK, which provides a nice graphical front end.

From the main Ubuntu desktop, then, go to "Applications" and then "Ubuntu Software Center." Choose "Edit" and then "Software Sources." You'll be presented with a box entitled, "Downloadable from the Internet," and you should be sure all four boxes are checked before you click on "Close."

Next, from the main Ubuntu Software Center page, click on the "Accessories" icon and type ClamTK into the search box. It will be shown as "Virus Scanner," but if you click on "More Info" you can verify it's the right package. Click "Install" and wait for it to download.

Once installation is finished, you should launch ClamTK by going to "Applications" in Ubuntu's main menu, then "Accessories" and "Virus Scanner," which is how the software will still be shown.

4. Run a scan

When the ClamTK window opens, click on the "Scan" tab and select the option for a Recursive Scan. Next, you'll need to tell the software which drive you want to check for viruses, which in this case is the one that includes Windows. Scanning may take some time, but once the infection is found you'll get the usual options for what to do with it, including quarantine and removal.

5. Return to normal

Assuming the infection has now been removed, your computer should be clean once again, making it safe to remove the LiveCD or USB and boot back into Windows as usual. As you enjoy your malware-free machine once again, remember that it's all thanks to Linux.

It's also not a bad idea to keep your LiveCD or USB handy so you'll be ready for the next time.