As it could be months before opening a crypto'd file has been locked (most ransom-ware only give you 48 - 72 hours to recover your data before deleting the private key) what sort of things can we put in place to stop this happening, besides a decent A/V and spam filter.
Você está fazendo tudo o que pode. Parece que a educação do usuário deve ser adicionada à lista.
It worries me that a few of these might slip through the net and there's nothing we can do once the machine is infected.
Backups regulares off-line são a única maneira de combater malware como o Cryptolocker. O Cryptolocker é apenas o começo.