Dark data is the untouched information stored in your systems—up to 55% of all...

https://sierra-wiki.win/index.php/How_Do_I_Report_on_File_Age,_Owner,_and_Last_Access%3F

Dark data is the untouched information stored in your systems—up to 55% of all data goes unused. This matters because it racks up costs and creates risk, especially when AI sifts through cluttered files