- You can change the port (default is 5900), by setting the keys use_alternative_port and alternative_port;
- You can reject connections from the network and allow only those from localhost (useful for who wish to exclusively use a tunneling mechanism to access the server, such as ssh), by setting the key local_only;
Keys mentioned above are located at /desktop/gnome/remote_access tree in gconf (You can use gconf-editor program)
We are in a discussion about to include or not these options in configuration applet (vino-preferences). If you have any opinion about this, let us know by commenting on bug 361891.