I'd pcap a bunch of the traffic -- in particular the DNS requests -- that will tell you where it is connecting. Hopefully it is using TLS, and then the SNI headers can give you more information.

I run a local DNS resolver and so I capture all the lookup responses so that I can turn IP addresses back into names. Depending on what firewall/router you have, you may be able to log connections. I use a locally hosted free Gravwell process to grab these logs and correlate with the DNS queries to find which systems are talking to where. If your home network is like mine, then there are probably a bunch of systems that you want to block from talking outside.

It may be worth sandboxing it into a dedicated network then analyze the traffic and see what it does in detail, for example if it accesses the local network then relays something outside, or if it opens ports waiting for connections, etc. I wonder if merely downloading so much data and storing it into its internal flash could wear it in a short time forcing the user to call for repair.

You can have fun with Wireshark https://www.wireshark.org/

Depending on the details in each of the layers[1] you might be able to spoof traffic towards it to trick it things.

you may need to try MITM the certs/key exchange stuff[2], hopefully they have a broken implementation that doesnt validate signatures etc.

[1]: https://www.bmc.com/blogs/osi-model-7-layers/

[2]: first promising hit when i googled: https://gbhackers.com/mitm-attack-https-connection-ssl-strip...

I wash Really hoping for some wireshark goodness in that thread!

Does it stop functioning intermittently? I've seen cases of devices in the middle of a failed OTA, and the device keeps requesting the OTA again. If it's going on and offline often, this might the case.

Have you tried tcpdump’ing its payload on your router? If it’s plain text it should be obvious what it’s doing. If it isn’t you can still sniff which domains it’s connecting to from SNI ClietnHello message but payload will be encrypted. You can still get to it but that would require some decent soldering and hw debugging skills…

If you have a openwrt router than it should be quite simple. Redirect the traffic from the ip of the washing machine to a machine that has mitmproxy installed (using iptables). Hopefully the protocol is https and it doesn't have some form of certificate pinning. That should get you the raw requests/responses.

What software/router do you have, that shows this upload/download graph?