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I neglected to mention that vnc is inherently insecure.
http://www.mit.edu/~avp/lqcd/ssh-vnc.html
So even if you try to never connect your Kobo to insecure networks, hosts, USB devices, etc., your host vnc server you are connecting to is still a security vulnerability. I would not use this host for anything critical. I would set a firewall and have the vnc server be read-only.
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