Syntax for NCrack is:
ncrack -U c:usernames.txt -P c:passwords.txt rdp://10.0.0.100:3389
Ncrack will only complete connections to a windows box if network level authentication is disabled.
You can tell if it is set to (more secure) if you add the -d10 switch to the ncrack command, you will see that each attempt results in an error.
