x11vnc allows one to view remotely and interact with real X displays 
(i.e. a display corresponding to a physical monitor, keyboard, and mouse) 
with any VNC viewer. In this way it plays the role for Unix/X11 that 
WinVNC plays for Windows.

It has built-in SSL encryption and authentication, UNIX account and 
password support, server-side scaling, single port HTTPS and VNC, mDNS 
service advertising, and TightVNC and UltraVNC file-transfer.

It also provides an encrypted Terminal Services mode (-create, -svc, or 
-xdmsvc options) based on Unix usernames and Unix passwords where the 
user does not need to memorize his VNC display/port number. See also 
the tsvnc terminal services mode of the SSVNC viewer.