Dark data is the information your company collects but doesn’t use or manage....

https://fast-wiki.win/index.php/What_Should_I_Do_with_Temp_Files_and_Legacy_Exports%3F

Dark data is the information your company collects but doesn’t use or manage. It often makes up 55% of data stored, leading to wasted storage and backup costs. Plus, it increases ransomware and breach risks since unmanaged data is harder to protect