The SAM and LSAD protocol implementations in Microsoft Windows Vista SP2 Windows Server 2008 SP2 and R2 SP1 Windows 7 SP1 Windows 8.1 Windows Server 2012 Gold and R2 Windows RT 8.1 and Windows 10 Gold and 1511 do not properly establish an RPC channel which allows man-in-the-middle attackers to perform protocol-downgrade attacks and impersonate users by modifying the client-server data stream aka \Windows SAM and LSAD Downgrade Vulnerability\ or \BADLOCK.\