Stopping you getting at your stuff
By now, you'll be familiar with the concept of Ransomware: something gets into your system; encrypts the files and demands payment to decrypt them again.
Lots of storage providers, notably Microsoft, are promising to prevent Ransomware from infecting your online storage - this seems to be on the basis of too many changes to too many files. I wouldn't just rely on this promise or my antivirus for protection but also make sure I have multiple backups that are offline and probably on external storage in a drawer somewhere.
You should always ensure your antivirus (yes and you Mac users), apps and operating system software are up-to-date. I know it's easy to disregard updates and put them off. Don't.
If you do fall victim to a ransomware attack - not that likely for an individual but possible - then you have to decide if you are willing to pay to get your stuff back. Just remember, you could pay and still not get it back. www.mailchimp.com
OneDrive and SharePoint
There have been reports of a flaw in OneDrive that allows the hacker to encrypt online files once they have gained access to the account - yet another reason to use strong passwords, never to repeat them and, ideally, use a password manager such as LastPass.
Some software that helps protect you against Ransomware by providing backup or detecting the the programs that do it:
Malwarebytes - a free scan: Malwarebytes Cybersecurity for Home and Business | Anti-Malware & Antivirus