Here’s what data Comcast says its motion-detecting routers collect

Comcast announced a new platform this week called Xfinity Shield that includes the option to let customers turn their routers into motion sensors. Many people reacted with fear and anger.

“I am not enabling this. I am also seriously considering replacing my leased gateway with my own equipment, because a device I do not control sitting in my living room measuring the motion of my family is not a feature I asked for,” wrote one customer on the r/Comcast subreddit

Some concerns stem from a clause on the support page for the feature, called WiFi Motion, which says Comcast might share motion-sensing data without notifying you if compelled by law. Others appear to stem from a distrust of Comcast.

The feature uses activity in Wi-Fi signals between newer Xfinity Gateways and connected devices to monitor motion in your home; it doesn’t use cameras, capture images or video, or record audio. However, it arrives amid a year of reporting on immigration unrest and how authorities obtain data from private companies like Flock. This has raised questions about who might be able to access the data it generates if you choose to turn on the free service.

The Verge asked Comcast what data WiFi Motion collects, how long it stores it, whether it shares it, and if so, under what circumstances. “When enabled by the customer, WiFi Motion keeps a record of motion activity within the Xfinity app up to 7 days,” said Comcast spokesperson Meagan Sloan via email. “Like all companies, should Comcast be served a valid subpoena, court order, search warrant or other lawful legal process, we may be required to disclose information generated by WiFi Motion consistent with applicable law.”

But customers also fear the feature could be enabled without their consent and worry about the types of information it was collecting.

We asked whether Comcast could remotely enable it if legally compelled, and whether it could view the data in real time — a scenario law enforcement could potentially use to determine if someone was in a home. Sloan said “WiFi Motion is opt in only by a customer,” and that “No, Comcast does not monitor customers’ motion activity or notifications in real time,” but did not say whether Comcast has the technical ability to do either.

Asked where the data lives, she said the company stores motion activity in its cloud system for up to seven days so users can view recent activity in the app.

The data includes motion event information that “indicate when movement is detected between a connected device and the Xfinity Gateway,” Sloan said. It also shows which Wi-Fi-connected device detected the motion.

For example, “Motion detected by LG TV” or “Motion detected by Hallway smart speaker.” The data does not include images, video, audio, or identifying information about people or pets, she added.

A pet sensitivity setting keeps pets under 40 pounds from triggering alerts, but it can’t specifically distinguish pets from people. Instead, it evaluates size. “Generally, larger objects create greater signal disruption, while smaller objects create less disruption,” said Sloan.

Comcast warns this is imprecise, especially for children under 40 pounds. So, it’s less accurate than a camera — but enough to tell whether someone was in the house, if not who.

Wi-Fi sensing can work through walls, and Comcast said its implementation requires fixed Wi-Fi devices that are always powered, so phones and laptops don’t count. You choose which devices detect activity during setup, which means it would theoretically be possible to follow someone through a home by watching which ones register motion.

Comcast says WiFi Motion is entirely opt in and something you can turn on or off, but if you’d rather not rely on the setting staying off, one option is to put your Xfinity Gateway into bridge mode and connect a third-party router. WiFi Motion only works between devices connected to the Gateway. If none are, it can’t detect anything.