How to NOT hide extensions in Windows

Part of theTrojan horse attacks help page

updated Sep 12, 2009

This file addresses the problem where Windows by default likes to hide theextensions of filenames, such that “britney.jpg” is shown as just “britney”.The danger is that “britney.jpg.exe”, which is an executable program, would beshown as “britney.jpg” which many would mistake for just a picture. This ispotentially very dangerous and confusing. It is the basis for many securityproblems such as viruses and Trojan horse attacks spread through the internetsuch as via email, IRC, IM, etc.

The solution is simple - just unhide the extensions.

• select the View tab
• check “show hidden files and folders”
• UNcheck “hide file extensions for known file types”
• Click OK to finish

If the above minimal directions are not enough for you, check out thisillustrated guide(external link).

IMPORTANT EXCEPTION:

Even after you unhide the extensions using the above steps, you still cannotsee certain hidden extensions for files ending with .shs, .pif, and .lnk(blame Microsoft for its infinite lack of wisdom). Unfortunately these filesare executable, and are rapidly becoming the most popular choices for manyTrojan horses, such as “Movie.avi.pif” which will look like “Movie.avi”, and“LIFE_STAGES.TXT.SHS” which will look like “LIFE_STAGES.TXT”. Instead of beinga movie and text file, respectively, they are both dangerous Trojans.

More Information

So now that you can see the extensions, how do you know which ones aredangerous? There are far too many to list comprehensively, so a simpler ruleis - when in doubt, don’t download or run the file. As the sayings go, don’ttake candy from strangers, and there’s no free lunch in life.