NLA (Network Level Authentication) is per default enabled since Windows 8 / 8.1 and Windows Server 2012.
Due to this option remote connection is refused if you try to connect from Linux client, iOSx (iPhone, iPad), Android devices, etc which do not support NLA.
If you are running Windows 8 Professional, Enterprise or Windows 2012 server you can easily uncheck NLA
"Computer" - right click "Properties" - "Remote Settings":
Unfortunately this user interface is not available with Standard version.
Here you have to modify the according registry key.
Open Registry-Editor (Start - Run - Enter: regedit) and move to path
HKLM\SYSTEM\CurrentControlSet\Control\Terminal Server\ Winstations\RDP-Tcp
in the right pane look for value "UserAuthentication" and change the value to "0"
(reboot required!)Tags: disable, Network Level Authentication, NLA, WIndows 7, Windows 8, Windows 8.1