The victim should contact their antivirus vendor. An antivirus support and response team can help customers in urgent cases. Also, antivirus vendors sometimes release tools that can rescue their customers if their customers have been infected. Many of the antivirus vendors provide tools that can decrypt ransomware encrypted files for a particular type of ransomware. Also, they provide tools that can remove boot infection, such as Petya. Sometimes these companies have an incident response team that can help the customers.