Dark data is the 55% of stored information left unused and unmanaged in your...

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

Dark data is the 55% of stored information left unused and unmanaged in your systems. It wastes storage and backup resources, costing companies up to $2.5 million a year. Left unchecked, dark data increases your risk of ransomware attacks or data breaches