Dark data is the information stored but not actively used, often making up 55%...

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

Dark data is the information stored but not actively used, often making up 55% of corporate data. This unused data increases storage and backup costs and raises breach risk by expanding your attack surface. It can also expose you to ransomware attacks