Windows NT4/2000/XP (9x/Millenium yalta's advanced mode)
Leaktest description
Yalta have two test : a classical test, and an advanced test.
The classical test try to send UDP packets toward ports often allowed, like
53 (DNS), 21(FTP), etc... in the hope to be allowed too.
The advanced test uses a driver to send his packets directly to network interface
in going under TCP/IP layer, to pass trough.
(advanced test under windows 9x/Millenium only)
Meaning
If the test is a success, this means that your firewall allows many kind of traffic
on pre configured ports.
default rule using, 
direct network interface reaching
