Dark data is the inactive information companies keep but don’t use—often 60-80%...

https://wiki-site.win/index.php/What_Should_I_Do_with_Former_Employee_Folders_on_the_File_Server%3F

Dark data is the inactive information companies keep but don’t use—often 60-80% of stored data. It increases storage and backup costs and raises breach risks, like ransomware targeting forgotten files