Let's see if I can give you a slight hint.
People all over the world have installed VNC (a server to view and control a remote computer) on lots of computers and made it possible to connect, and potentially control, them from any other computer on the internet.
Can you see the issue..?
(If not, please install VNC on your computer and make it accessible from the internet and wait and see if something "fun" happens to it. (This is a joke, please don't do this.))