A well thought out and implemented backup system, along with a good security setup is how you deal with malware. If backups won’t protect you from malware then you’re doing backups wrong. A proper backup implementation keeps a series of full backups plus incremental backups based on those full ones. So say your data doesn’t change very often, then you might do a full backup once a month and incremental ones twice a week. You keep 6 months of the combinations of full & incrementals, you don’t just overwrite the backups with new ones.

If you’re doing backups like that and you suffer a malware attack then you have the ability to recover data as far as 6 months ago. The chances you don’t discover malware encrypting your data for 6+ months is tiny. If you’re really paranoid then you also test recovering files from random backups on a regular basis.

My employer has detected and blocked multiple malware attacks using a combination of the above practices plus device management software that can detect unusual NAS activity and block suspect devices on our networks. Each time our security team was able to identify the encrypted files and restore over 99% from backups.

I have literally lost all data on a RAID6 of 12 drives since the power distributor in the server (the bit between the redundant PSUs and the rest of the system) got fried and took 5 out of the 12 drives with it.