Use a Non-apple VNC Client or Server
You might not be able to get all the security, configuration options, or cross-platform compatibility you want from the VNC software that Apple distributes for Panther, Tiger, or Leopard. You have alternatives.
Mac OS X users have two straightforward choices for installing VNC (both client and server): Chicken of the VNC, and Vine Viewer. Chicken of the VNC is free for use as a client or server; Vine offers a free server, but charges $35 per copy (after an evaluation period) for its client software.