this post was submitted on 04 Oct 2025
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Why do my LG smart fridge and my GE washer and dryer all have DNS servers? And is there a way I can control them without the manufacturer's miserable apps? (lemmy.radio)
submitted 4 hours ago by early_riser@lemmy.radio to c/homeassistant@lemmy.world
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First thing I do when I get a smart appliance is scan it with nmap. This has revealed some interesting Easter eggs, like my Davis instruments air quality sensors having a local REST API.

Doing the usual scan against my GE washer and dryer shows that port 53 is listening. What could that be for? Is there a way I can at least query their status locally or something?

When I got the washer and dryer I was excited about the smart home features because getting an alert when my laundry is done or starting the washer remotely so the clothes are done when I get home are genuinely useful features. However, last time I checked the app none of that was available, so I just have these Trojan horses in my home spying on me with no benefit in exchange. Their app wanted my freaking mailing address when I signed up for their mandatory account, so the features mentioned above are the least they could offer in exchange for my digital soul. But I digress.

My fridge is in a similar situation. It commits the additional cardinal sin of ONLY being controllable via the app, with no on-board temp or filter status indicators whatsoever.

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[–] the_q@lemmy.zip 4 points 47 minutes ago

No one needs "smart" appliances. I know it's fun to get a message telling you your water filter needs replacing, but come on...

[–] fubarx@lemmy.world 1 points 40 minutes ago

Most appliances connect using a cheap microprocessor like an ESP-32 which provides both WiFi and BLE.

If there's a DNS server running, it's usually for mDNS/ZeroConf service discovery. Usually so it can easily get provisioned via a smart speaker or hub.

More details here: https://circuitlabs.net/dns-server-and-dns-sd-implementation/

[–] Zwuzelmaus@feddit.org 31 points 4 hours ago* (last edited 4 hours ago) (1 children)

First thing I do when I get a smart appliance is scan it with nmap.

A wonderful habit. I will try to copy it from you :)

About your main question, I can only guess that it's for the initial setup of these appliances. Initially, they know nothing about your Wifi situation. So maybe they open up their own Wifi and connect their app so that you can enter some info. Afterwards, maybe some services continue to run there...

[–] IphtashuFitz@lemmy.world 17 points 4 hours ago

You mention it’s listening on port 53, but have you actually tried DNS queries to see how it responds? Will it resolve www.google.com or <reverse_ip>.in-address.arpa?

[–] r0ertel@lemmy.world 13 points 4 hours ago

A port scan and then inspection of the ports is a great habit. Another fun thing to do is to set up WireShark to listen to what your fridge's IP address is doing. Who is it calling? How often? What services (ports)? While your fridge may have a DNS server, unless it's been pre-loaded with the internet, it'll need to query another DNS to reach the outside world. DNS is usually unencrypted, so you can see what it's asking to connect to.

Many of these devices announce their services via Bonjour or whatever protocol. It's a way for devices like Alexa to find out that you have a printer, interrogate the printer and then Alexa will tell you that your printer is low on ink and by the way, Amazon has a special sale, just for you.

If anything is unencrypted, check it out (with WireShark). If it is encrypted, there's a chance that you can hijack it with a proxy server. Set up a SOCKS proxy and add a DNS label (I can't remember what it is) to tell the devices in your network that you have a proxy. Block the fridge from the internet and see if it will autodetect the proxy. There are other ways to tell devices that your home network requires a proxy via autodetection & wpad.dat files in specific locations on your network. You can configure your proxy to log all traffic, like WireShark does and then see what's in the payload.

I've done this with limited success on various devices. More mature products like Alexa are locked down. Those cheap home cameras from China are pretty hackable.

Have fun!

[–] Oisteink@lemmy.world 3 points 4 hours ago (1 children)

Both tcp and udp?

[–] early_riser@lemmy.radio 6 points 4 hours ago

Washer dryer and fridge are TCP only