Like dropbox? I would expect the malware to encrypt it like any other folder, you will just have encrypted files in the cloud. Unless your provider gives you incremental backups.
It will, but AFAIK Dropbox keeps data for 30 days (or can get a yearly thing). I don't know if it's possible to rollback the entire stash though, nor do I know if there's a limit in the number of updates.
> Unless your provider gives you incremental backups.
I would really hope most cloud services either do that or only push verified files (for software-specific clouds) in which case the encrypted files would fault the application and not be uploaded or downloaded.