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Excel workbook protection and sheet protection are commonly used as if they provide file security. It turns out that these mechanisms do NOT provide file security, nor were they ever intended to do so. Section 18.2.29 of ECMA-376-1:2016, the latest version of the standard governing Office Open XML, says the following:
Applications might use workbook protection to prevent anyone from accidentally changing, moving, or deleting important data. This protection can be ignored by applications which choose not to support this optional protection mechanism.
The same section contains an additional note:
Worksheet or workbook element protection should not be confused with file security. It is not meant to make your workbook safe from unintentional modification, and cannot protect it from malicious modification.
Both sheet protection and workbook protection may be removed without the protection password in four basic steps:
- Unzip the .xlsx or .xlsm file so that its contents may be modified in the following steps. Excel workbook files are actually ZIP files with a different file name extension.
- Remove the <workbookProtection ... /> XML tag from the xl\workbook.xml file.
- Remove the <sheetProtection ... /> XML tag from any .xml file in the xl\worksheets\ directory.
- Zip the modified Excel workbook file contents, using the .xlsx or .xlsm filename extension for the resulting ZIP file.
I have published a detailed PDF guide for accomplishing these steps using only File Explorer and Notepad on Windows.
Is anyone else surprised by how easy it is to bypass these protections?
(Score: 2) by EJ on Tuesday July 09 2019, @02:12AM
There actually is a way to do this:
4. Make the content available only via an online file, like Google Docs. Sure, you can make a copy of that file and edit it all you want, but everyone who goes to access the file will still only ever see the original.