File type checking in OS X
By using Finder in Column View you can get an idea of how Mac OS X will open a file if it is double clicked.
Often, virus and worm authors will trick users into executing harmful code through social engineering. They enticing the user by providing them with a file or a link that promises to be interesting or important.
In this example, we see two file with the same .jpg file extension and the same icon. However, by using the Kind column, we can see that Malicious.jpg is not a JPG Image as expect, but rather it is a Terminal Document -- a script that could be used to compromise your computer. Any number of "Safe" files (such as .mov .pdf .zip) can be saved in this malicious way.
You can also determine the Kind of file by selecting the Get Info option from the File menu of Finder.
References:
Critical Vulnerability Adobe Acrobat and Reader
