I have an ISP supplied cable modem/router over which I have almost no control. T

Question

I have an ISP supplied cable modem/router over which I have almost no control. They can upgrade the firmware remotely, so I assume they can do virtually anything with it.

When I transfer data using the switch that is contained within the modem, I think they could look at the data. When I use my own switch which is connected to the ISP modem, will the ISP modem see the traffic that goes through the switch?

I know WiFi that is secured with WPA2-PSK can be eavesdropped upon, same as BNC-style network or those old CAT-style hubs I had in 2000. That is the source of my confusion/suspicion.

Explanation / Answer

A switch will try to only send traffic to its intended recipient. But it is not guaranteed. If the switch doesn't know where the recipient is, it will send the packet to all devices connected to the switch.

There are ways to make a switch forget where the intended recipient is (such as overflowing the CAM or MAC spoofing).

There are also ways to make individual computers send packets to some other MAC than the intended recipient (ARP spoofing and the like).

You should only consider a switched network to be a trusted network if you either trust every device connected to the network or the switch has some advanced security features to protect against all the attacks described above.

You'd be better off using a router, which is controlled by yourself only. If using your own router would mean an (extra) layer of NAT, you should use a bridging firewall instead.

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