How ‘Free' Wi-fi Hot Spots Can Track Your Location Even When You Aren't Connected
PCWorld|December 2018

Simple steps can protect your privacy and location data.

Dieter Holger

Before you join the Wi-Fi hotspot at your local cafe, you might want to make sure it won’t follow your footsteps—literally—after you leave.

Ostensibly “free” Wi-Fi hotspots are in hundreds of thousands of businesses and public spaces across the United States. They’re in shopping malls. In airports. In chain restaurants. In local cafes. As a result, it’s easier than ever to get online. If your notebook or phone lacks a reliable data connection, you can still connect to a hotspot. But this convenience often comes at a price: your personal data and privacy.

When you use “free” Wi-Fi, there’s a good chance it’s managed by a third-party provider—which gets you online in exchange for your valuable sign-on data. The sign-on information that hotspots require will vary, but often includes your email address, phone number, social media profile, and other personal information. All can be used to target you with advertising and gain insights on your habits.

As Emory Roane, policy counsel at Privacy Rights Clearinghouse (go.pcworld. com/part), told PCWorld: “Read through the Wi-Fi Terms of Use for any of these businesses and you’ll almost certainly realize that there’s still no such thing as a free lunch.”

That’s probably not a surprise to most Wi-Fi hotspot users. But what might surprise you is that some hotspot providers are taking data collection a step further, and quietly tracking millions of users’ whereabouts even after they’ve left an establishment. These hotspots are part of America’s burgeoning location-based Wi-Fi marketing industry.

PCWorld spoke to privacy experts and Wi-Fi location-analytics companies to learn more about how this technology works, and what you can do to avoid being tracked.

WI-FI LOCATION TRACKING AND YOU

PCWorld reviewed the privacy policies (go. pcworld.com/pvdc) of a dozen Wi-Fi hotspot providers and found that they commonly ask users to agree to location tracking when they sign on. Some phrases that tip off this practice are “location data,” “location history,” “your location,” “device identifiers,” and “MAC address” (more on this later).

We reached out to all of the Wi-Fi companies, but only two with major operations in the United States responded to questions about tracking hotspot users. These networks, Zenreach (go. pcworld.com/zenr) and Euclid (go.pcworld.com/ ecld), log the locations of millions of smartphone and laptop owners who pass within range of their hotspots— even when these people don’t sign on.

According to Zenreach’s privacy policy, “Later, when the user’s device returns to this client location or enters the Wi-Fi range of another Zenreach router (of any Zenreach client), we automatically recognize the device and record the visit in our record for that device.”

According to Euclid’s privacy policy, “General Visit Information is collected as your mobile device moves across different Locations that use our technology.”

To give you an idea of a hotspot network’s scope, Zenreach counts Peet’s Coffee, Five Guys, IHOP, and KFC among its larger clients, according to its website (go.pcworld.com/ znwb). KFC has nearly 4,500 locations nationwide, so these networks can span broad swaths of urban areas.

HOW IT WORKS: DATA COLLECTION BEGINS AT THE CAPTIVE PORTAL

When you connect to public Wi-Fi, you’ll usually be greeted with a sign-in form, also known as a “captive portal.” This is where you provide personal information and consent to terms of service to get online.

In the case of Zenreach, “by clicking ‘go online,’ you agree to our terms of use and privacy policy,” allowing them to track your location over time. Euclid is more explicit, saying, “you agree to provide this device’s location” next to where you can tick a box to consent.

What distinguishes location-based marketing hotspot providers like Zenreach and Euclid from standard third-party hotspot providers is that the personal information you enter in the captive portal—like your email address, phone number, or social media profile—can be linked to your laptop or smartphone’s Media Access Control (MAC) address. That’s the unique alphanumeric ID that devices broadcast when Wi-Fi is switched on.

As Euclid explains in its privacy policy, “... if you bring your mobile device to your favorite clothing store today that is a Location—and then a popular local restaurant a few days later that is also a Location—we may know that a mobile device was in both locations based on seeing the same MAC Address.”

MAC addresses alone don’t contain identifying information besides the make of a device, such as whether a smartphone is an iPhone or a Samsung Galaxy. But as long as a device’s MAC address is linked to someone’s profile, and the device’s Wi-Fi is turned on, the movements of its owner can be followed by any hotspot from the same provider.

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