If you have sensitive data you'd like to keep from prying eyes in a Microsoft Excel file, the easiest way to protect it is with Excel's built-in password tools.

Crisis averted–kind of. Permission to copy the entire workbook is another problem. For instance, if you open a protected Excel file in the browser edition, you can see hidden formulas.

Sending Excel files containing crucial financial and business data has risks. To add a layer of protection, you should learn to password protect an Excel file.