Unfortunately most of these decryptor programs are after the fact. It's no big deal to alter the algorythm used to encrypt program and data files. On the other hand IF you have the time, it''s posible to break the encryption using common phrases and the like to do substitutions until you crack the encryption, or law enforcement catches up and makes the perps reveal the current code and the algorythm used to facilitate it. The former can take some time and I suspect that's partly what Avast has done along with being supplied with the decryption code of companies that paid fhe ransom. Many don't.
The big thing now is moving everything up to the cloud starting with data files which admittedly slows things way down. Eventually if the company converts to a remote SaaS (Software as a Service) basically everything is remote and isolated from the users network, leaving only comparitively trivial items exposed on the local network LAN.
Some governmemt agencies have been using this model for decades and it works quite well. What it boils down to no matter how stupid your users are or how vulnerable your WAN hardware may be, you're not really touchable. These ransomware attacks will become as ineffective as the DDoS attacks have become with smart routers that discriminate calls from the public facing IP. I have seen the anti-DDoS hardware at work and it's some pretty clever stuff.
