Windows 7 RC is now available, but even though they have fixed multiple bugs and vulnerabilities, it seems that they may have forgotten one. A vulnerability has recently been brought up in Windows Explorer that lets viruses hide executable files, some security researchers say.

Some of the nice people over at F-Secure have found a major vulnerability in Windows Explorer. According to their post, it looks like anyone that makes a virus can disguise it as another file type, fooling you into clicking something that may seem like a harmless picture, but turns out to be an executable file that destroys your hard drive. The way the file name is structured takes advantage of the fact that Windows Explorer hides file extensions by default. So what may seem like horrible_malware.txt is actually horrible_malware.txt.exe. Confused? Here is an example:

Looks like a simple text file, right? Well, let’s see what happens when it is opened:

Here’s how you can make sure you don’t get tricked. Open any Windows Explorer window, or click on the folder icon in your superbar. Press Alt, select Tools, then Options from the menu.

Then click on the View tab, and make sure Hide extensions for known file types is unchecked. Then press OK.

Keep in mind that you can now easily change file extensions since they are no longer hidden. Changing a file’s file extension can make the file unusable. Generally, file extensions should not be changed or erased at all. Windows does warn you with a prompt window when the file extension is changed.

As always, be careful with what files you download and always equip your computer with anti-virus software. Alternatively, you can also scan the file using a major online virus scanner such as VirusScan.Jotti or VirusTotal.

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. Read the rest at windows7center.com.