The "WannaCry" ransomware of the past day or two was, amusingly, mitigated by private citizens without Government involvement. The malware had a built in "Kill Switch", where if it was able to talk to a website at a domain, it would quit. That domain was not registered, so a lovely chap registered it and pointed it at a webserver... Stopping the malware spreading.

I doubt version 2 of this malware will have such a kill switch...