Dark data is the unused or forgotten information stored in your systems, often...

https://www.echobookmarks.win/dark-data-is-the-information-your-company-collects-but-never-uses-about-55-of

Dark data is the unused or forgotten information stored in your systems, often making up 55% of your data. It’s costly because it wastes storage and raises security risks. For AI projects, dark data adds noise, slowing down results