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.

Open the spreadsheet you want to protect in Excel, click the "Review" tab and then click "Protect Sheet" in the Changes group to display the Protect Sheet dialog.

If you would like to make sure that your Excel spreadsheet data is secure this guide will show you how to password protect and hide worksheets ...

Spreadsheets created or uploaded to Zoho Docs can be shared -- and protected -- in much the same way, with the added benefit of password protection when sharing documents with non-registered users.

You can lock cells in Excel by heading into the program's "Protection" tab. There, you can set a password, and protect your data.