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Windows 7

View File Extensions

SUMMARY: To help prevent against opening rogue files with double extensions, enable viewing file extensions from Explorer.

By default, Windows 7 hides the file extensions of known file types in Explorer views. The reasoning - this keeps the display clean, as often a file's icon signifies its type.

However, as in in Windows Vista and earlier, this default setting is a potential security risk. It's possible that you can receive a file via e-mail with an extension of ".txt", or a file with a Notepad icon. Unfortunately, this file could have a hidden second extension, meaning that if you double-click the file, you may actually execute spyware or other malware instead!

Don't just take my word for it - Anti-virus and security software developer F-Secure describes this problem as well in their blog.

Luckily, the "fix" for this is easy:

1. Click the "Start" button, type folder options and click the "Folder Options" link that appears.

Accessing Folder Options from the Windows 7 Start button

2. When the "Folder Options" multi-tabbed dialog box appears, click the "View" tab.

3. Uncheck "Hide extensions for known file types".

4. Click "OK" to close the dialog box.

This tip was written for Windows 7 RC. Screenshots and information are subject to change between this and the official release of Windows 7.