Smart TVs, cars and other devices
Why it matters More and more of your life is watched by devices that have no screen of settings you ever look at: the TV, the car, the speaker in the kitchen. A network log can tell you a lot about them, but not everything, and knowing the gap keeps you from false comfort or needless worry.
Smart TVs: recognising the picture
ACR (automatic content recognition): a TV feature that takes small samples of the picture or sound, turns each into a short code called a fingerprint, and sends it to a matching service that works out what you are watching.
Think of a friend who glances at your TV every few seconds and texts a description to someone with a huge catalogue of shows. They never need to know where the picture came from: a streaming app, live TV, a games console or a laptop plugged into the HDMI port all look the same to them.
In a capture, ACR has a recognisable rhythm: small requests to the same matching service, every few seconds, for as long as something is on screen. Our project capture includes a practice TV whose ACR service is acr.glance.example, sending a field called acr_fp.
Cars: the phone you cannot see
Telematics: data a vehicle collects and sends about itself and its driving, such as location, speed, braking and mileage.
Many modern cars carry their own mobile connection, like a phone built into the dashboard. That matters for this module: the car's data goes over the mobile network, not through your home Wi-Fi, so nothing on your network log will ever show it. Driving data can interest others, such as insurers, which is why the sharing settings in a car's menu or its companion app are worth reading.
Voice assistants: listening for one word
A smart speaker listens all the time, but only for its wake word, and that listening happens on the device itself. After it hears the wake word (or something it mistakes for it), it sends the audio that follows to the company's servers. In a capture you see that as a burst of upload right after you speak, and much less the rest of the time.
What a network log shows
- Who: the names of the companies a device contacts.
- When and how often: the ACR rhythm, a nightly upload, traffic while the device is supposedly "off".
- How much: a few hundred bytes per minute is a ping; megabytes is something bigger.
- Changes: whether traffic to the ACR service stops after you switch ACR off. That is the best test of a setting you have.
What it cannot show
- Contents: the data is encrypted, so you see envelopes, not letters (unless you intercept, which TVs and cars rarely allow).
- Other paths: a car's own mobile connection, a phone on mobile data, Bluetooth to a nearby phone.
- Later: data stored on the device and sent another day or from another network.
- After the server: who the company shares or sells data to, or which records it joins together.
A common misconception
"I switched the TV's ACR off, and the log still shows traffic, so the setting does nothing." TVs contact their makers for many reasons: updates, the app store, the time. The question is whether traffic to the ACR service stopped. Compare the same service before and after, not the total.
Try it Open your home router's page or app and find the list of connected devices. Note which ones you recognise. On your TV, search the settings for "viewing information", "ACR", "interactivity" or "smart features" (the name differs by brand), and switch it off (checked October 2026). If your router or DNS filter shows per-device lookups, compare one evening of TV traffic before and after.
Recap
- ACR identifies what is on screen from samples of picture or sound, whatever the source.
- Cars often send telematics over their own mobile link, which your home network never sees.
- A network log shows who, when, how often and how much, but not contents, other paths or what happens after the server.
- To test a setting, compare traffic to the one service it controls, before and after.
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