There are types of Office documents that you should NOT open, even if they come from someone you trust. Here’s the full list of file extensions for the older Office document formats which are much more likely to be ‘malicious’ docs from hackers and criminals.
We’ve talked about the risks of receiving hacked documents using the older Microsoft Office document formats. Hackers generally use the common .doc .xls or .ppt documents but there are others. Bad documents are sometimes put inside .zip files or fake .zip’s.
The ‘new’ Microsoft Office document formats (‘new’ means 2007!) are much safer with in-built protections against running hidden code.
To the human eye, it’s easy to tell old and new formats apart. All the older formats have 3 letter extensions (.doc) while the new formats have 4 letter extensions (.docx). Access 2007 and later use 5 letter extensions (.accdb etc).
Use this list if you’re making Outlook Rules or VBA to check for attachments using the older formats.
See Why Old Office documents should be banned
Word
.doc
.dot
.rtf isn’t just an Office document format but it was widely used in past decades. It also can be used to run nasty code on your computer and should be treated with caution.
Excel
.xls
.xlt
.xlm
.xla
.xll
.xlw
.slk
PowerPoint
.ppt
.pot
.pps
Access
.mdb
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