Dark data is the inactive or unused information that piles up in your...

https://www.normalbookmarks.win/dark-data-is-hidden-information-your-company-keeps-but-rarely-uses-about-55-of

Dark data is the inactive or unused information that piles up in your storage—up to 60-80% of it. This data not only wastes money on storage and backups but also increases your risk of ransomware attacks and data breaches