PC users who are updating to the Windows 10 operating system are being warned about fake update emails coming from an address that looks like it is Microsoft. The emails have an attachment that contains ransomware and will encrypt the user's files or lock up a computer, demanding $500 in bitcoin to unlock data. "Windows users should understand that Microsoft will never send patches via email, but rather use their internal update utility embedded in every current Windows operating system," writes Karl Sigler, threat intelligence manager at Trustwave SpiderLabs.