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.

An icon in the shape of a lightning bolt. Impact Link If you want your Microsoft Excel spreadsheet to have a little more protection, you can encrypt its data by ...

XLS files are Excel workbook files created in Excel 97 or Excel 2003. The 2007, 2010 and 2013 versions of the program use the XLSX format by default to save workbooks, but can also use the XLS format.