VNC isn't known for being the most secure...
If you only need the command line, take a look at things about ssh. A good ssh client for Windows is PuTTY.
If you need the GUI, you could tunnel VNC through a ssh, which is quite secure. If you're interested, let me know, I have a site with good instructions on how to do this somewhere in my mess of bookmarks...
Lastly, you could configure your VNC server to use a different port... might get you in trouble though
Hope this helps!