Since you updated to iOS 13 or iPadOS 13, you may have seen a message appear when you’re away from a Wi-Fi network you’ve joined previously. “Available Wi-Fi Network: ‘Name of Network’ is an available network nearby.” A Join button may appear or you may need to tap the notification to get one to show up.
The first time I saw this, I wondered if a malicious party had finally figured out a way to make an illegitimate message somehow appear on my iPhone. Then I remembered this somewhat obscure bit of text at Apple’s announcement of the new operating system updates:
Popular Wi-Fi networks. Your iPhone determines which Wi-Fi networks at your location are being used and notifies you if one is available.
That’s it. No other descriptive text. I’ve got a good guess about what’s going on.
IDGMeet popular networks in your area!
From a user standpoint, it’s handy to not scan through huge lists of Wi-Fi locations that often appear now everywhere you go in public and be presented with the one most people are connecting to. Getting a pop-up that suggests the most likely network or networks you would use bypasses that. I like it.
Now for the guess. Apple is likely scanning “probe requests,” which is something you probably don’t know every Wi-Fi device you own routinely does. A “probe request” is a list your device sends out of every network it’s ever connected to before. Any matching Wi-Fi gateway that “hears” this responds to start up a connection.
Your device can listen to a bunch of these probe requests, which are sent in the clear and without any protection, and then compile that into a list of the most popular.
(If you don’t want your device to create these probes, disable Wi-Fi whenever it’s not in use.)
These probe requests are distinct, by the way, from your device’s scans for active Wi-Fi gateways around it. These scans look only for messages broadcast by Wi-Fi gateways and a laptop, mobile device, or other Wi-Fi hardware relies on those broadcast to assemble a list of potential networks that they might join.
Apple, Google, and others also routinely uploads this list at regular intervals—depending on your opt-in settings—along with the recorded signal strength of each gateway, associated with GPS coordinates and other device-based location information, to help fine tune positioning of your devices, especially in areas with weak GPS or cellular reception.
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Author: Glenn Fleishman, Senior Contributor
Glenn Fleishman’s most recent books include Take Control of iOS and iPadOS Privacy and Security, Take Control of Calendar and Reminders, and Take Control of Securing Your Mac. In his spare time, he writes about printing and type history. He’s a senior contributor to Macworld, where he writes Mac 911.