Dark data is the information your business collects but never uses, often...

https://www.phone-bookmarks.win/dark-data-is-the-inactive-or-unused-data-stored-across-your-systems-often

Dark data is the information your business collects but never uses, often making up 55% of stored data. It creates storage and backup costs that can reach millions annually and increases ransomware and breach risks by expanding your attack surface