Dark data is all the information your company stores but never uses—like old...

https://telegra.ph/What-Are-Common-Examples-of-Dark-Data-in-IT-Departments-07-31

Dark data is all the information your company stores but never uses—like old emails, logs, or files gathering dust. It can be up to 60-80% of your data, quietly eating up storage space and costing you money—sometimes $2.5 million a year