Outlook on the web is now blocking another 38 email attachments because they can be carriers of viruses. But Microsoft doesn’t block the most commonly used files for infecting computers.
Far and away the most common infected email attachment is old-style Word documents, with .doc extensions. Excel .xls worksheets and PowerPoint .ppt presentations are similarly risky but not as regularly used by hackers.
The main carrier of virus infection is Microsoft Office documents, a fact that Microsoft doesn’t like to talk about. They try to hide that by talking about a ‘malicious Word document’ without making the important distinction between a .doc and the safer .docx format.
Block .doc .xls .ppt ?
The reason why the older Office documents aren’t blocked:
- Complaints from users. If .doc were blocked, customers would complain they can’t get files they want. Sadly, the older document formats are still being used. Any decision to block email attachments is balanced against the inconvenience to users.
- Microsoft’s embarrassment. Blocking the older doc formats would be an admission of the ongoing problems with the formats that Microsoft championed and defended for many years.
Trust no .doc .xls or .ppt documents
Our advice is to treat any .doc .xls or .ppt files with great suspicion. Don’t open them.
If they come from someone you know, politely ask them to resend in a safer, and smaller, format.
What has Microsoft done?
The newly blocked attachments are files that could be used to infect computers, though the risk is relatively low.
Most of the attachment types are obscure or obsolete. Many were made by Microsoft in the first place.
A few are more likely to annoy developers and administrators, for example Windows PowerShell scripts will be blocked.
It’s a long list which we’ve made into a sortable and searchable table.