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

https://www.animenewsnetwork.com/bbs/phpBB2/profile.php?mode=viewprofile&u=1217505

Dark data is the inactive or unused information that builds up in your storage—often 60-80% of what you keep. It increases your risk of ransomware attacks and data breaches because it’s overlooked in security scans