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I want to check for viruses on a computer that I suspect may be infected with malware.

Its users are running an antivirus, but there's always the risk that something slips past and the way I see it, once the system is infected the antivirus is useless because the malware can hide itself from the AV.

I think the best way to go (besides clean reinstall of the OS) would be to have an antivirus running at a boot time from a CD or a USB key. That way, the malware is just lying on the disk and cannot do any of its hide-and-seek stuff (provided the AV comes from an uninfected PC and all that).

So, I'm looking for something that:

  • Runs at boot time (off USB key or CD-ROM)
  • Does not touch or require the local OS
  • Discovers malware fairly well (like, Avast, AVG, Norton, whatever -- I think the're all the same anyway)
  • Can handle Windows filesystems (FAT 32, NTFS, WinFS ;-) )
  • Comes from some sort of trusted source (no Windows Antivirus 2009)

I know that this is no silver bullet (nothing is, really*), but I do have a feeling it's more likely to help than doing the scan* within the infected system.

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5 Answers

There's a tutorial here to install the Antivir Rescue CD from Avira on a bootable USB key. It's running on Linux, with r/w support for NTFS.

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This seems interesting, thank you. –  Tomas Sedovic Sep 7 '09 at 21:09
    
There is a newer (2009) version of the article at: askthegeek.kennyhart.com/index.php/2009/05/14/… Unfortunatelly, both contain broken links to the rescue CDs. Still, the guide should help for other CDs as well. –  Tomas Sedovic Sep 7 '09 at 22:29
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a-squared Emergency USB Stick

according to AV-Test.org, a-squared's scan engine (Ikarus) sports a very high detection rate.

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Looking at the site, it doesn't do bootable USB does it? I suppose I could do a bootable FreeDOS and run the commandline version though... –  Tomas Sedovic Sep 7 '09 at 21:06
    
It requires Win32 system to run, so I can't use it for a boot-time scan. –  Tomas Sedovic Sep 7 '09 at 21:58
    
of course you can, boot BartPE (CD or USB stick), it will detect your USB stick and then use it from there. or copy A2CMD onto your BartPE USB stick (WinToFlash helps a great deal if you prefer USB over CD). –  Molly7244 Sep 7 '09 at 22:36
    
Okay, my bad :-). This sounds interesting, I'll give it a try. –  Tomas Sedovic Sep 8 '09 at 10:42
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I have a dual boot setup with Windows 7 on one partition and Ubuntu 9.10 on another.

I think your theory has merit. I wonder how it might affect a situation like mine were I to become infected? Given that they are vastly different OSs, I would guess that it would be EXTREMELY unlikely for a virus (say from Windows) to infect my Linux installation, even thought they share the same physical drive.

As for the AV software, from all my research on numerous sites, the general consensus seems to point toward: (1) AVK, (2) Avira, (3) Avast!, (4) BitDefender, (5) AVG being the top five best AV software out there (roughly in that order). Unfortunately the best of them is the only one that doesn't offer a free version.

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unetbootin has a bunch of AVs as options. You might also be able to use it to mount antivirus ISOs onto a bootable USB.

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Ultimate Boot CD for Windows aka UBCD4Win

A bootable recovery CD (or USB disk) that contains software used for repairing, restoring, or diagnosing almost any computer problem.

It's based on Bart's PE (a Windows "pre-install" environment CD, basically a simple Windows® XP booted from CD) and have many useful plug-ins (built-in or not). So, you have to build it with a XP cd, but the builder is user friendly enough and that let you customize the bootable media...

It includes multiple virus scanner (Avira, Kaspersky Virus Removal Tool, Superantispyware, Malwarebyte's Antimalware). They basically all does the same thing, but they doesn't get the same results... So, I think it's better to use minimum two engine. (And go in the plug-ins section to update them before creating the boot cd)

It have a big community and exists from long time enough to be trusted.

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