Petya ransomware overwrites the master boot record (MBR) of affected PCs, leaving their operating systems in an unbootable state. The MBR is the code stored in the first sectors of a hard disk drive and launches the operating system’s boot loader. Without a proper MBR, the computer doesn’t know which partitions contain an OS and how to start it. The ransom message instructs users to access the attackers’ decryption site on the Tor anonymity network and provides them with a unique code that identifies their computer.”]