Philadelphia is kicking off 2019 with a brand new public WiFi system, LinkPHL—a network of digital kiosks in Center City and University City launched by Mayor Kenney’s office just before the holidays.

The kiosks, called Links, offer a range of services at no cost to taxpayers or users, including “super fast” WiFi, device charging, domestic phone calls, access to city services, maps and directions, and information about community and arts events. December’s launch was the first of 100 Links to be rolled out in Philly.

But how is it possible that all of these services are free?

Like Facebook and Google, LinkPHL makes its money by selling ads. However, unlike internet companies, LinkPHL gathers data on people in public spaces to do so.

We need to think critically about the trade-offs that this business model introduces and its implications for our city.

As research for a book about smart cities, I studied LinkNYC, LinkPHL’s predecessor in New York City. Given that both systems are operated by the company Intersection, there are a couple things that Philadelphians should know about the kiosks.

Like the New York system, the Links in Philadelphia are equipped with cameras. Civil rights advocates in New York were disturbed by the cameras’ surveillance implications. In response to complaints, Intersection updated its privacy policy to better specify its use of the footage.

LinkPHL uses a privacy policy similar to New York’s. It states that footage captured on the Link kiosks is only held for seven days, that the company will hand over footage to law enforcement in the event of a crime, and that it “will not use facial recognition technology for any reason” or “use the cameras to track your movement throughout the city.”

But when you use the WiFi service, the Links do collect and retain a large amount of information about you for up to 60 days, including the type of device you’re using, your MAC address (an encrypted version your device’s identification number for WiFi networks), your IP address, your browser type and version, your browser plug-ins, and your operating system.

In its privacy policy, Intersection designates all of this information as "technical” rather than “personal.” But there is plenty of evidence to suggest the data can be used to learn a lot about you—beyond what your name or email address could tell them.

For example, according to a patent owned by an executive at Intersection, the company can use encrypted information collected about your device to identify that someone is a returning customer at a store, that they’re running late, that they’re at a sports event or concert, or that two devices belong to people who regularly appear together, such as couples or co-workers.

All \this information is incredibly valuable to marketers or advertisers—Intersection’s real clients. Each Link is equipped with 55” LED screens that display ads. Intersection can capitalize on user data to tailor those ads, reassure marketers that people from preferable demographic categories are being exposed to the messages, and charge more for ads that display during busier times or when wealthier audiences are nearby. As the privacy policy states, the information the Links gather can be used to “deliver relevant advertising on public displays” and “enable measurement of the effectiveness of advertising.”

Why is this important? It reflects a growing privatization of our cities’ public spaces.

As Intersection’s website states, one of its missions is to “transform the urban experience." Citizens need to be involved in this transformation.

Sidewalks may still be common throughways, where chance encounters and political protests take place. But if we’re trading away our privacy, anonymity, and the right to be left alone in public, then we deserve to be part of the conversation. We need to be aware of trade-offs between access and surveillance, and to think critically about what they will mean for the future of our city.

Aaron Shapiro is a Philadelphia native and a researcher and lecturer at the Annenberg School for Communication at the University of Pennsylvania. His book Design, Control, Predict: Logistical Governance in the Smart City, is in preparation for the University of Minnesota Press.