Dark data is the inactive or unused information that piles up in storage—often...

https://blogfreely.net/samuel-wang09/what-is-kappa-data-services-and-why-is-it-tied-to-python

Dark data is the inactive or unused information that piles up in storage—often 60-80% of total data—yet still creates risks like ransomware exposure and contributes to $2.5 million in annual storage and backup costs