File extensions are typically a 3 character extension on the end of a file, started with a dot. For example, a typical executable file in Windows is .exe.

Sometimes you may never know this because file extensions are hidden in Windows. I typically prefer to leave the extensions on so I know what type of file I'm dealing with. To make file extensions show, go to Windows Explorer or My Computer. At the top of the screen to go Tools, Folder Options, then click on the View tab, and uncheck where it says hide extensions for known file types.

In just a moment we'll see why having file extensions showing is important. Lets first look at what a file association is. A file associate tells the operating system what program to use to open a particular file extension. For example, a common file extension for pictures is .JPG. A JPG or JPEG is a compressed file format for picture files. There are several programs that will open these files. For example, I could use the Windows Picture Viewer, Adobe Photoshop, Macromedia Fireworks, and a wide array of other programs. Typically when you install a program, it will ask you (and sometimes not ask you) if you want to associate certain files with their program. Thus, sometimes it's necessary to change what program you want opening a certain extension. To change the file association for a extension go to Windows Explorer or My Computer, go to Tools, Folder Options, then click on the File Types tab. In the list below you will see almost every type of file extension you will encounter. After highlighting the desired extension, you can click the change button below, and browse to the program you want those files to be opened with. Aside from graphics files, a common extension people want to change is a .MP3 file. For example, you may want your MP3 files to be opened with iTunes rather than Windows Media Player, or perhaps Winamp. It's up to you!

Now that we know what file extensions and associates are, let me tell you why this is important to have file extensions showing. Commonly when people produce viruses, they hide them with known file types such as .MP3, however the file is really an executable like .exe or a .bat file. Here is what they'll do. They'll name the file: myweddingpics.jpg.exe. You see, they make it look like a JPEG, but it's really not. If you had your file extensions configured not to show, all you would see is myweddingpics.jpg. Thus, you may click on it because you think it's a picture, but really you just installed a virus hidden in a clever disguise. To most computer professionals, this is easy to recognize, but it's a common tactic to fool the average computer user.

I hope this article has shed some light on how you can manage your file properties in a greater capacity, and by using this empowerment, make you more secure.