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Dangers of File Swapping via Removable Media

Posted on May 10, 2011
Just because files are on a CD or a USB thumb drive doesn't mean they are safe. Removable media is a great way to spread malicious software like viruses, Trojans and spyware. Learn the dangers of file swapping with removable media and how to avoid getting — or transmitting! — viruses.
Tags: usb virus

With the advent of tiny, "keychain" USB drives, it's easier than ever to swap files between computers, even if they aren't networked. Just copy files to the drive, hand it off to a friend or business associate, and voilà: files transferred.

There's just one problem, though. Because removable media is a great way to swap files, it's also a great way to spread malware like viruses, Trojans, and spyware. Learn the USB virus dangers and how to protect yourself from them.

Removable Media is More Dangerous Than the Internet

There are several reasons why computer users should be aware of the dangers of transferring files via USB and other drives. The simplest reason is that removable media, such as CDs, DVDs, and USB and Firewire drives (thumb, flash, jump, pen), appear innocuous. Most people are aware of the dangers of getting infected via networks — whether a company's intranet or the Internet itself — and keep antivirus software running to safeguard against viruses coming over these networks. However, when someone hands them a keychain USB drive with Excel spreadsheets they just created, they might be tempted to just copy those files off the removable media without question.

The primary virus danger of removable media is that it bypasses firewalls and network antivirus checkpoints automatically. For instance, ISPs run antivirus software on their email servers in order to catch and quarantine infected emails before they can infect you, the user. If that same virus is hidden in a file on a USB drive, it's getting a free ride past that checkpoint. Same goes for the firewall in your computer. Firewalls are configured to catch suspicious files trying to reach your computer through the Internet, not to catch suspicious files trying to reach your computer through your USB port.

Ways Your Computer Can Get Infected From Removable Media

If a USB drive given to you contains infected files, those viruses can easily be transferred to your computer because of how removable media bypasses firewalls and network checkpoints like email server scanners. Here are some ways your computer can get infected.

Viruses, worms, and Trojans will piggyback or infect legitimate or legitimate-appearing files and get copied onto your own computer when you transfer the files from removable media to your computer. Opening or running the files will activate the malware, which may do one or more of several things. In some cases, malware takes advantage of "autorun"-type features. One memorable instance of this was the Autostart Worm of 1998, which infected Apple computers, because it was and remains the most successful attack on Macs to date. The Autostart Worm replicated and spread via removable media — Zip disks — and took advantage of Apple's CD Autoplay feature, which came enabled in the operating system by default, in order to run itself.

Once a piece of malicious software is running, it might do one or more of these things. It might install a rootkit hidden in the user's operating system whose purpose is to keep the virus from being eradicated. It might install spyware to track your activity. It might make your computer a "zombie" in a botnet, in which someone else can use your computer to unscrupulous ends — for instance, to send spam emails. Or, it might install a keystroke logger on your computer, which catches every character you type and is used to discover and steal your passwords, financial information, and more.

Protect Yourself From File-Swapping Viruses

Whether the removable media is CD, DVD, Firewire or USB, virus scanning software can help protect you from infecting your computer. Other ways to help prevent getting viruses from keychain drives and the like include knowing your source, and not swapping illegally-obtained files.

When deciding on an antivirus program, be sure to look through each application's feature list to make sure that it includes tools to guard against this type of threat. In particular, it's a good idea to invest in a product that lets you schedule and run regular scans of your system in addition to scanning files as you upload them to your computer. That way, if a virus does manage to sneak through with the initial file transfer, the software can catch and eradicate it during a scheduled scan.

Now you know the dangers, so there's no excuse for being unprepared — protect yourself from the potential dangers of removable media.

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