I'm using a dynamic DNS service provider that gives me a URL to access, and based on the IP address accessing that URL my dynamic hostname gets updated with that IP address. This is being run from a NAS device I have that is plugged in directly to the wireless router (with an Ethernet cable).
My question is whether someone who is on the network (or even not on the network) using tools like Wireshark or other methods find that URL I'm accessing? It's a plain HTTP URL not HTTPS, if that makes any difference. Because if they can, they can access it from another device and change my hostname to have an incorrect IP address. (I'm not asking so much because I'm worried about the consequences of someone doing this, I'm asking to help increase my understanding of how these things actually work.)
Does it make a difference whether they are connected to the same wireless router directly (with an Ethernet cable), or whether they're accessing its WiFi? And does it make a difference if that WiFi has a password or doesn't?
Btw, how about the case where the NAS isn't plugged in directly to the device, but is plugged in to my laptop using a crossover Ethernet cable and is accessing my laptop's internet connection to access that dynamic DNS URL, who would be able to see that URL?