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If there is malware on the flash drive, it could very well be in the files from that drive that you are copying to your computer.

Hi. I work at a public school and was told that today my computer has a virus. I don't know how this came to be. Could my flash drive have created this virus? I'm constantly inserting and ejecting my flash drive from one computer into another. Can a flash drive transfer viruses? It makes me feel as if I've done something really bad.

First, getting a virus doesn't neccessarily mean you've done anything really bad. It happens to people all the time.

Flash drives can transfer viruses. From the situation you're describing, yes, you might have passed one on to a computer that you're using.

Viruses and flash drives

Is your flash drive dangerous?

Viruses can be written such that they will use flash drives to transfer themselves to other computers. It's actually a very common mechanism for some forms of malware to infect other machines. It's important to realize that and to understand that when you transfer a flash drive from one machine to another, you may very well be carrying malware with you.

To avoid this kind of thing in the future, I would suggest that you do two things.

Check out your anti-malware software

The first thing to do is make sure that any machine that you plug your flash drive into has:

  • Up-to-date anti-malware software

  • Access to the software's latest database of known threats

  • Settings for periodic scans. The machine should also be running these scans regularly.

That's important to basically detect and catch any malware that may actually be on those machines.

Turn off Autoplay or Autorun

The other thing is to turn off autoplay on all of your machines. Autoplay or autorun is that thing that automatically detects that you've inserted a flash drive or a CD or a DVD and automatically runs a program to do something with the device you've just installed.

Malware writers have been able to take advantage of that.

They set the flash drives up so that when they are inserted, auto run kicks in and automatically runs the malicious software that's on the flash drive. And that malicious software then obviously infects the machine.

Sure, turning off autoplay, autorun, or any auto features may make things a little bit more inconvenient. You actually have to manually start playing your CDs or manually start playing your DVDs.

But the good news is then that you don't have to worry about flash drives automatically infecting you.

Always on the lookout for malware

Flash drives can still carry malware. It's still a possibility. In fact, if there's malware on the flash drive, it could very well be in the files that you've carried in the files that you yourself are copying. This is a start. This is an important aspect of making sure that your flash drives and your computers in general are safe.

Article C6398 - April 14, 2013 « »

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Leo Leo A. Notenboom has been playing with computers since he was required to take a programming class in 1976. An 18 year career as a programmer at Microsoft soon followed. After "retiring" in 2001, Leo started Ask Leo! in 2003 as a place for answers to common computer and technical questions. More about Leo.

Not what you needed?

April 16, 2013 10:01 AM

Back in the days before the IBM PC and networks became popular, the hot bed of virus spreading were the Apple IIs and Macs because many schools had them in labs for anyone to plug their floppy disks in and use. The viruses would use the floppy disk the same way current ones can use a memory stick so that they would infect the next computer that it was plugged into.

If you work at a school (assume that students and many teachers are not careful at all about viruses) check with your IT people to find out if they are doing anything to block viruses. You live in a dangerous environment for them.

Ken B
April 16, 2013 10:37 AM
Sure, turning off autoplay, autorun, or any auto features may make things a little bit more inconvenient. You actually have to manually start playing your CDs or manually start playing your DVDs.
Note that newer versions of Windows (at least 7 and 8 -- I don't recall about Vista) allow you to select the types of disks which will have autorun enabled. In other words, you can tell Windows to auto-play a music CD, or a movie DVD, but to "do nothing" or "ask what to do" for anything else.
April 22, 2013 10:47 AM

If you're able to, sometimes you can set the drive to read-only. If the drive's already infected it won't stop it from spreading to machines, but it can prevent drive from getting infected in the first place, especially plugging into unknown machines. (Of course, only if there's no need to actually write to the drive.)

May 11, 2013 9:38 AM

When I used to use AVG, I noticed that buried in the preferences there was an option to scan removable media. By default, it is turned off.

I turned it on and believe me, it's the best security decision I ever made. It saved my bacon several times after I plugged in a USB flash drive and it scanned it automatically.

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