Dark data is the inactive or unused information stored across your...

https://www.bookmarking-jet.win/dark-data-is-the-information-your-company-collects-but-never-uses-often-making

Dark data is the inactive or unused information stored across your systems—often 60-80% of your data. It matters because it increases storage and backup costs, sometimes wasting millions annually, and raises breach risks including ransomware exposure