Dark data is the information your company collects but doesn’t use, often...

https://www.bookmark-belt.win/dark-data-is-the-unused-information-stored-by-companies-often-55-or-more-of

Dark data is the information your company collects but doesn’t use, often making up 55% or more of your stored data. It increases storage and backup costs and raises breach risk since outdated data can be a prime target for ransomware