Prevent hidden sheets in ThisWorkbook to be visible by using a macro and run from another workbook-CodePudding

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However, nobody can use such a protected file without the password. And once you give them the password then everything is accessible because:

A Workbook protection, as the one I suggested in the initial answer under Review/Protect Workbook, can easily be 'cracked' by saving the file in the old .xls format and then simply removing it (no prompt for password). Same is applicable for Worksheets. Also, a brute force VBA macro could achive the same thing on older versions of Excel. Also, the internal files (under the Excel file archive) can be edited to remove the passwords

The VBA project password can be cracked in at last 2 ways:

if opening the file with an archiver then one can edit the DPB=.. entry under \xl\vbaProject.bin\PROJECT

by using a macro to hook the password dialog via Win API

The suggestion I made in this answer only prevents 'normal' users to unhide the hidden worksheets but that does not stop more 'advanced' users to copy the information from those sheets via macros and most certainly does not prevent them to crack the passwords.

If you want total security on those hidden sheets then you should move the data outside of the Excel file as suggested by @SolarMike in the comments