98% of computers hit by WannaCry were running Windows 7
According to a report by cybersecurity firm Kaspersky Lab, over 98% of the computers hit by the global WannaCry ransomware attack were running some version of Microsoft Windows 7. The infection distribution on Windows XP computers was "insignificant", according to Kaspersky's Director of Research Costin Raiu. As for Windows 10, the malware was limited to testers and manual infections.