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

https://www.apu-bookmarks.win/dark-data-is-the-inactive-or-unused-information-organizations-keep-but-don-t

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