When opening downloaded files, always pay close attention to their extension. Beware of files with multiple extensions; these are often used to hide dangerous Trojan horses (computer viruses) that could seriously damage your system or others.
For example, imagine you downloaded a file named:
music.mp3.exe
Note that the final extension is the actual extension of the file, that is, the 'mp3' is NOT the file's extension, it is 'exe'. This means that although you might think the file is an mp3 file, the file is actually an executable, and if you were to double-click on it, instead of hearing music in your audio player, you would actually be running a program that could cause great harm to your computer.
By default, Window hides the extensions of filenames, so that "music.mp3" is shown as just "music". The danger is that "music.mp3.exe", which is an executable program, would be shown as "music.mp3" which could be easily mistaken for a harmless music file. One way to avoid these problems is to follow these simple guidelines:
