The quickest method to get back your mission-critical files after a ransomware attack (e.g. WannaCry) is to restore from the recent backup. Therefore, after regularly backing up your data with CloudBacko to your NAS, FTP / SFTP server, or public cloud storage, no ransomware can threaten you.
CloudBacko is an affordable VMware / Hyper-V backup solution with enterprise-class features such as Instant VM Recovery, Live Migration, Granular Restore, etc. If you are using ESXi free version, the corresponding add-on module is even free of charge!