A researcher has developed a tool that allows victims infected with the Petya ransomware to unlock their files for free. The tool exploits a mistake made by the ransomware’s author in the way that the ransomware encrypts a file on a Windows machine, opening opportunities for the decryption key to be determined. The researcher, who operates the Twitter handle @leostone, announced the tool over the weekend. Currently, the ransomware demands 0.99 BTC (approximately US $418) from its victims.”]
Source: https://grahamcluley.com/petya-ransomware-unlock-tool/