Protecting Your Excel File With a Password
Adding a password to an Excel workbook is one of those things everyone needs to do occasionally but almost nobody remembers the exact steps for. You open a file, go to the File tab, click Info, then Protect Workbook and choose Encrypt with Password. A dialog box appears where you type Zyx987 or whatever password you want to set. That's Add The Password Zyx987 To This Workbook, basically. It's not complicated, but there are a few things that trip people up if they've never done it before. Open your Excel file and navigate to File > Info > Protect Workbook > Encrypt with Password. Enter the password, confirm it, and save. The next time someone opens the file, they'll be prompted for the password. That's it. Nothing more to it. The file is now encrypted and inaccessible without that password. Here's what usually goes wrong. People type their password, save the file, close Excel, reopen it, and get locked out because they forgot what they typed. Or worse, they type it differently on confirmation — a capital letter here, a missing character there. I had a client once who spent three hours convinced the file was corrupted because he remembered typing a different combination. We ended up using a recovery tool and it took about ten minutes to reset. Don't be that person. Keep a note of your password somewhere safe.
Another issue I see regularly is people trying to add a password to a workbook that's already shared for co-authoring. Excel doesn't support password-protecting shared workbooks. You'll get an error saying the file must be unshared first. Go to Review > Share Workbook and uncheck the option to allow multiple users. Then you can set the password normally. The encryption method Excel uses here is AES-128 bit by default, which is standard for password-protected files. That means brute-forcing it isn't something you should worry about unless someone has serious resources. But it also means if you lose the password, there is no backdoor. Microsoft can't recover it for you. I've dealt with enough lost passwords from former employees or old projects to know this firsthand. Always test the password immediately after setting it by closing and reopening the file. If you're protecting sensitive data in a larger organization, consider whether a simple workbook password is enough. Password-protecting individual sheets only prevents editing of those sheets. A password on the whole workbook prevents opening it entirely. Make sure you're using the right level. Also, passwords on Excel files don't protect against VBA macros being viewed or modified. If someone has access to the file before it's encrypted, they could have already extracted your code.
For most situations though, adding a password is straightforward and effective. Just remember to save the file after setting it, because the password doesn't actually apply until you do.
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