Dark data is the information companies collect but never use or classify—often...

https://qqpipi.com//index.php/What_Are_Transparent_File_Tables_and_Why_Do_Data_Engineers_Care%3F

Dark data is the information companies collect but never use or classify—often 55% of all stored data. This unused data not only racks up storage costs, sometimes wasting over $2.5 million annually, but also creates risks like security gaps