A group of American boffins have devised a system dubbed Crypto Drop that working with a save what you can approach is able to defeat all ransomware. The countermeasures are triggered once the ransomware start encrypting files, the experts demonstrated that it is possible to block it when it had encrypted just 0.2 percent of files on the infected machine. The technique relies on three primary indicators of the ransomware activity: Bulk modification of file types; Dissimilarity the encrypted file looks nothing like the plaintext; Entropy encryption should produce consistency high entropy in its output.”]
Source: http://securityaffairs.co/wordpress/49312/malware/crypto-drop-defeated-ransomware.html