The vast majority of systems affected by the WannaCry ransomware were running Windows 7, according to data published by Kaspersky.
Kaspersky’s Costin Raiu tweeted data showing that over 98% of WannaCry victims were using versions of the Windows 7 operating system.
More than 60% of affected users were running Windows 7 64-bit.
According to Kaspersky’s data, more Windows 10 users were affected by the WannaCry ransomware than those running Windows XP.
Microsoft issued a security patch on 14 March which protected users against the attack, although many users did not install the update and remained vulnerable.
— Costin Raiu (@craiu) May 19, 2017