We've blocked ~12,000 malware attacks today utilizing this exploit and our threat team recommends -- along with keeping your security software fully active and up to date -- to also ensure that your Windows systems are fully patched and up to date.
I think it's also important to note this variant of Petya isn't actually ransomware, since it doesn't save the private key the data is pretty much not retrievable, so it's more of a wiper.