Dark data is the inactive or unused information your business stores but...

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

Dark data is the inactive or unused information your business stores but doesn’t analyze. It can make up 55% of your data and often hides risks like ransomware exposure. Plus, storing and backing up this data wastes money—sometimes over $2