The Wannacry cyber attack earlier this month targeted Windows 7 more then any other Windows operating system. Microsoft had sent out a security up-date in March that dealt with this security glitch; so any machine that was on MS's security updates were not effected. MS also sent out to other MS OP's; beside those already on security up-dates; the fix; to Windows XP, Windows 8, and Windows Server 2003; customers.
This is one of the reasons Windows users should up-grade to Win 10 if their OP can't be updated; or if they can; keep their machines on Windows update.
This is one of the reasons Windows users should up-grade to Win 10 if their OP can't be updated; or if they can; keep their machines on Windows update.