Several users (myself included) have gotten "Heads up!" emails from Sharepoint, saying that a large volume of files have been deleted. The files have been deleted, and it's typically a lot of files, in a 15-minute burst. But it's also happening at times when the user is not online and not logged in. (I can say with some certainty--it happened on my computer at 615a, before I had even turned my computer on for the day).
These 'ghost deletes' are extremely alarming--they are happening for folders and files outside of those typically accessed by users.
Office 365, Exchange license, 34 users (most part-time and semi-active), I'm the company administrator. Not finding anything on Google.