In The Trust Center - File Block Settings

In essence, these settings tell Word, Excel, PowerPoint, and Visio: “When you encounter a file saved in [X format], do not let the user open it—or, at the very least, do not let them save to it.”

| File Type | Extension | Risk Level | Recommended Action | | :--- | :--- | :--- | :--- | | | .xlm | Critical | Hard Block (Open & Save) | | Word 2 / Word 6.0 | .doc (pre-97) | High | Hard Block | | Excel 95 Workbooks | .xls (pre-97) | High | Hard Block | | PowerPoint 95 | .ppt (pre-97) | Medium | Protected View | | Web Pages | .htm , .html | Medium | Block Open (they trigger scripts) | Group Policy: Managing at Scale The worst way to manage File Block Settings is by walking to each desk. The best way is via Group Policy Administrative Templates (ADMX/ADML). file block settings in the trust center

Set File Block Settings to "Open selected file types in Protected View" . Users can still view and copy-paste data, but they cannot edit or save. This forces them to consciously choose "Enable Editing" and then "Save As" a modern format. In essence, these settings tell Word, Excel, PowerPoint,

If you have ever tried to open an old .xls file from 1998, received a corrupted .pptx , or watched a user panic because an email attachment opened as a wall of garbled text, you have witnessed File Block Settings in action. Users can still view and copy-paste data, but

Use PowerShell to scan network shares for .doc , .xls , and .ppt files. Identify who owns them and when they were last modified.

Modern ransomware campaigns specifically target older formats because security tools often scan new .docx files rigorously but ignore a .xls file from 2003. If you are in IT support, you know the ticket. A senior executive tries to open a 15-year-old budget file. They see: "Microsoft Excel cannot open or save any more documents because there is not enough available memory or disk space." (This error is a lie. The problem isn't memory; it is the File Block Settings.)