Microsoft Malware Protection Center (MMPC) published a blog post yesterday detailing a new ransomware infection that appears to have begun in Ukraine and spread from there to other places in Europe and beyond. MMPC analysis showed this to be a more sophisticated variant of Ransom:Win32/Petyaand all free Microsoft antimalware products were updated with signatures for this threat, including Windows Defender Antivirus.
Read about it on the Azure blog.