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

https://www.slideserve.com/aaron_ward92/why-does-dark-data-create-operational-drag-for-it-teams

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