Even if your users are completely trained to never open Word files with funky extensions, dangerous documents can come disguised with a friendly ".doc" extension. The May Patch Tuesday included an update that fixed a hole in Word relating to malicious RTF and HTML files, says a post in the Microsoft Security Vulnerability Research & Defense blog. However, if your users don't use, or rarely use, Word to open RTF or HTML documents, you may be better off blocking those files from loading in Word altogether. The SVRD blog posted instruction on how to do that.

It is important for users to realize that an RTF or HTML document that has a ".doc" extension will still successful open up in Word as the originally formatted document. So changing the extension doesn't change Word's ability to read the formatting contained in the document. If your users do have legitimate reasons to open RTF or HTML documents in Word, you can limit your exposure to any potential malware by specifying "a trusted (Office 2007) or exempt (Office 2003) folder" so that files loaded from that specified folder are always opened, but those that come from other, unknown places are not, the SVRD blog describes

Here are some links that explain how to enable File Block and also how to configure trusted/exempt folders:

• For Microsoft Word: http://support.microsoft.com/kb/922849
• For Microsoft Excel: http://support.microsoft.com/kb/922848
• For Microsoft PowerPoint: http://support.microsoft.com/kb/922847

 

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