In computing, x11vnc is a Virtual Network Computing (VNC) server program. It allows remote access from a remote client to a computer hosting an X Window session and the x11vnc software, continuously polling the X server's frame buffer for changes. This allows the user to control their X11 desktop (KDE, GNOME, XFCE, etc) from a remote computer either on the user's own network, or from over the Internet as if the user were sitting in front of it. x11vnc can also poll non-X11 frame buffer devices, such as webcams or TV tuner cards, iPAQ, Neuros OSD, the Linux console, and the Mac OS X graphics display.
x11vnc does not create an extra display (or X desktop) for remote control. Instead, it uses the existing X11 display shown on the monitor of a Unix-like computer in real time. x11vnc has security features that allows the user to set an access password or to use Unix usernames and passwords.
It has options for connection via a secure SSL link. An SSL Java VNC viewer applet is provided that enables secure connections from a web browser. The VeNCrypt SSL/TLS VNC security type is also supported.
Many of the UltraVNC extensions to VNC are supported by x11vnc, including file transfer.
More info here http://en.wikipedia.org/wiki/X11vnc