Comcast's router can now tell when someone walks past it

Your router can sense someone crossing the room. Not as a figure of speech: the radio signal between an Xfinity gateway and, say, a smart speaker on the far shelf changes measurably when a body passes through it, and Comcast has been quietly testing that since 2024.

It went live on 18 August as WiFi Motion, one piece of a bundle called Xfinity Shield. The free tier, WiFi Shield, comes with any Advanced Xfinity Gateway at no extra cost: movement alerts in the Xfinity app, malware and phishing blocking at the network level, and screen-time controls for the household. Shield Select runs $15 a month and adds an indoor camera that distinguishes people from pets from packages, a door and window sensor, cloud video storage and a 24/7 emergency response line.

The motion part involves no camera at all, which is genuinely the appeal - it covers rooms you'd never put a lens in, and there's nothing to charge. Comcast says it detects movement rather than identifying anyone, and doesn't track where in the house that movement happened. The feature is opt-in and stays off until you turn it on.

The paperwork is less reassuring. As BleepingComputer pointed out, Comcast's terms let it hand the resulting data to third parties "without further notice" in connection with law enforcement requests or disputes, and there's no published answer on what gets stored or for how long. That's not a reason to skip it. It is a reason to read the screen before you tap through, because a running log of when your home is empty is a sensitive thing to start generating.

Worth knowing what's on your network regardless - Tendvane's network scan lists every device currently connected to your Wi-Fi, and it's usually a longer list than people expect.