I can’t tell you how often I have to repair an infected computer because someone was overly trusting in [insert latest file sharing program]. Programs like LimeWire are the victims of much hate and while these types of file sharing are popular with people who want to infect your computer, it’s usually very easy to avoid these infections with good habits.

No matter what file sharing software you use or even just downloading files from websites and our email, you’re at risk of getting a virus at some point. The best thing we can do is train ourselves to do a few very important things every time we download…

Check the file type

Before starting a download or opening a file check what the file types/extensions are. Is the file an .AVI, .MP3 or.EXE? It’s important to know what file extension goes with the type of file you’re downloading and to not run the file if you see something unexpected.

Here is list of some common file types and extensions:

  • Video: .AVI, .MPG, .MP4 and .MKV
  • Audio: .MP3, .OGG and .WAV
  • Image: .JPG, .JPEG, .BMP
  • Document: .DOC, .DOCX, .TXT and .RTF

An “.EXE” is an “executable file” or a “program”, Windows users should be extra cautious when working with these files as they are NOT movies, music or pictures. Often malicious people will try to confuse you by making a virus file named something with multiple extensions like: “the_file_i_want.avi.exe”, it’s important to remember that only the last extension is relevant.

Windows computers might be configured by default to hide all file extensions for files on the computer (files already downloaded). You can either change that option or view a file’s full name (and additional information) by right clicking on it and selecting ‘properties’ from the menu.

If you don’t recognize a file type or the file you want has a file type that doesn’t make sense then don’t download it or run it.

Check the file size!

Before downloading or opening a file check how large it is. Viruses are normal small (less then 1 MB), so if your trying to download a song that’s 3 minutes long, but the files is only 50KB then we know that its not the song we want. Most often a song will be at least 1MB a minute. If we try to download a 5 minute movie clip and the file is 1MB then we know its not our movie, our movie should be at least 10MB. Photos are a little more tricky, because they are the perfect size to use as a disguise, so just pay closer attention to the other indicators.

Some websites and developers of very large software (like Norton Antivirus or large frequently updated video games like World of Warcraft) use a “downloader”, “updater” or “download agent”. These very small programs run on your computer in order to handle the download process for the rest of the software. Only use these download agents if they came from a very trusted source, many websites have an alternative download link that doesn’t utilize their download agent.

When Your’e Done, Your Done

Sharing is great, but if your’e not very familiar with the file sharing program and the files you’ve downloaded, you should remove the listing for the file from within the program, it will still be in your downloads folder but wont continue to be uploaded. You should also close (not minimize to tray) the file sharing program when you are done using it.


It goes without saying that antivirus software is important but when did you last check to make sure it isn’t expired or the virus definitions outdated?