Dark data is unused information that often sits idle—about 55% of enterprise...

https://www.echobookmarks.win/dark-data-is-the-inactive-or-unused-information-that-builds-up-in-your

Dark data is unused information that often sits idle—about 55% of enterprise data remains dark. This dormant data poses a real breach risk if hacked and adds unnecessary storage and backup costs, which can exceed $2.5 million annually