In this white paper, we present a new attack vector against the Windows Single Sign On (SSO) feature of Microsoft Windows, leveraging the venerable Microsoft Server Message Block (SMB) protocol, affecting all versions of Windows, including Windows 10. While attacks involving SMB have long time been common in local networks, this new attack allows complete user compromise from the Internet. By leveraging a series of bugs and malfunctions, we shall see how remote redentials theft or user impersonation an be performed with minimal user interaction, extremely reliably, and from the Internet. This is in particular believed to be the first attack against Windows 10 and its web browser Spartan. Finally, we will contemplate a strategy to contain the problem at perimeter level and why it is doomed to largely fail, as well as suggest additional hardening to remediate this vulnerability more consistently at host level.