VNC Listen Mode: Random "Connection Failed Invalid Protocol"

[AnswerPhone]

We are using VNC Listen Mode 1.2.2.4 without the DSM plugin. Several times per day we get a random series of popups: "Connection Failed - Invalid Protocol". We have port 5500 open and forwarded to the PC that has the listening agent active on it. It seems to be triggering from a random port scan out on the internet.

Is there a way to prevent these popups besides turning off listening mode until you're expecting an inbound remote connection?

[Bonji]

You'd have to implement something on your side to filter/block the port scans. You can limit what IPs can connect or just turn off access in the firewall until it's needed.

I'd HIGHLY suggest you use encryption if you're going to make that service available directly on the internet. Also, I would block the connection from the firewall and not just shut down the VNC program, as the latter still allows them to communicate directly with your computer at any time.