It is low, Shodan has found more than 10,000 VNC that have disabled authentication:<p><a href="https:&#x2F;&#x2F;www.shodan.io&#x2F;search?query=rfb+authentication+disabled" rel="nofollow">https:&#x2F;&#x2F;www.shodan.io&#x2F;search?query=rfb+authentication+disabl...</a><p>And there are roughly 550,000 VNC servers on the Internet:<p><a href="https:&#x2F;&#x2F;www.shodan.io&#x2F;search?query=rfb" rel="nofollow">https:&#x2F;&#x2F;www.shodan.io&#x2F;search?query=rfb</a>