Ransomware is a form of malware that restricts access to data on infected computer systems. It generally propagates as a trojan, where the file initially seems to be legitimate, but can take on different forms. Some types restrict access to an infected computer, others systematically encrypt files on a system’s hard drive. No matter the style, a ransom is extorted to regain access to the data, typically in a digital currency such as bitcoin or pre-paid cash vouchers.