IOS 10 warning: Using a hidden network can expose personally identifiable information

Question

I am aware that 'hiding' a wifi network/SSID does not make the network MORE secure, but Apple's warning on IOS 10:

Using a hidden network can expose personally identifiable information

seems to indicate that hidden networks are LESS secure.

Clicking the 'learn more' link does not give any further info supporting the claim.

Exactly how can hiding an SSID make the network any LESS secure (by "expose[ing] personally identifiable information")

Answer 1

Clients that connect to known networks automatically will advertise “hidden” SSIDs in all of their probe requests. This results in your device broadcasting those SSIDs everywhere you go, to anyone who’s listening.

This behavior is dependent on the client’s operating system. For instance, you can configure Windows 7 and later to not connect to hidden networks automatically (only “visible” ones). That prevents such broadcasts from happening, but then you have to connect to hidden networks manually every time.

On the other hand, iOS and macOS always connect to known networks, hidden or not. The fact that iOS 10 warns about this would indicate that Apple has no plans to add the kind of toggle switch that Microsoft added in Windows 7, or to force the user to connect manually. Therefore, iOS and macOS constantly broadcast all the hidden SSIDs they are capable of connecting to.

Microsoft explains this behavior on TechNet:

A non-broadcast network is not undetectable. Non-broadcast networks are advertised in the probe requests sent out by wireless clients and in the responses to the probe requests sent by wireless APs. Unlike broadcast networks, wireless clients running Windows XP with Service Pack 2 or Windows Server® 2003 with Service Pack 1 that are configured to connect to non-broadcast networks are constantly disclosing the SSID of those networks, even when those networks are not in range.

Therefore, using non-broadcast networks compromises the privacy of the wireless network configuration of a Windows XP or Windows Server 2003-based wireless client because it is periodically disclosing its set of preferred non-broadcast wireless networks.

Now as to why this is a privacy issue:

1. You are potentially revealing SSIDs to a lot of people. Those SSIDs may include first and/or last names, which I’ve seen people use in network names.
2. Should I point out the irony of broadcasting an SSID in the direct vicinity of the access point trying to hide it? But instead of just having your AP broadcasting its SSID, every client in range does. Then the AP responds to each of those clients with the SSID itself.
3. Someone with a database of SSIDs could figure out where you’ve been or where you spend your time—possibly even where you live and work, based on your SSID broadcast beacons. Knowing where you live and work could lead to figuring out who you are, or at least identify you among a group of wireless clients (since your broadcasts might be unique to you).
4. This information, acting as a signature, could allow malicious individuals to track your comings and goings. If you carry your phone with you everywhere you go, then someone with a large-enough network of radio receivers could know where you are at any given time.

Sound far-fetched? Criminals/advertisers/the government have done worse things. MAC addresses were once used to track shoppers’ movements through malls. Apple subsequently randomized MAC addresses in probe requests.

Thankfully, no one I know has used a hidden SSID in well over a decade, and I haven’t seen that practice recommended in about as long.

Update: Since there seems to be some confusion as to why you can’t connect to a hidden network without broadcasting it to the world, as well as about security vs. privacy, let’s make a fun analogy.

Imagine a driver (the AP) is picking you up from the airport. They don't know you, and you don’t know them. So they hold up a sign that reads, “John Doe.” When you find them, you (the client) go and tell them, “I’m John Doe.” This is what happens when connecting to a broadcast network.

Now, imagine that driver is trying to be super covert, and doesn’t hold up that sign. What happens now is you have to walk around yelling, “Who’s picking up John Doe?” over and over, until finally the driver steps forward and responds, “I'm picking up John Doe.”

In either case, you then exchange credentials, make sure you’re each who you think you’re dealing with. What happens after authentication is just as secure either way. But every step leading up to it compromises your privacy.

Answer 2

Preface

I think what Apple's message on your screenshot wanted to say is that hiding networks' SSID won't allow them to hid anything except that. So basically they're telling you hiding networks isn't safer it just doesn't broadcast the SSID.

I agree with you the message can be very tricky to interpret, but I see this as the only reasonable way to read that. But let's not desperate, it's still a Beta, Apple changes a lot in Beta versions, so hopefully they'll update and clarify this message as well!

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Thus, as Apple wrote on that page it suggested you:

Hiding a network doesn't secure your Wi-Fi network, because the SSID is still available through other mechanisms. Security is enforced by a different setting.

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End of the story

Hiding networks' SSID won't make them safer or more secure.

Answer 3

The only thing I see here is that if you are hiding your SSID, then the device (IOS or windows) must query for the SSID on a regular basis to determine if it is in range, even if it isn't. This means that your device will broadcast everywhere were the SSID cannot be reached.

If you however turn on your SSID as broadcast, then the device will passively 'listen' for the SSID instead of constantly broadcasting it.

I have problems with my wifes IPhone 5 on my home hidden SSID since she upgraded to windows 10 and I think it is because Apple has changed it so that it does not continually broadcast for hidden SSIDs. I have no problems at all with any of the android devices I use or with any of the windows devices either... and after a quick scan, it appears they do not broadcast for the SSID (They broadcast for all SSID's and then choose from the list). It appears to be an Apple specific issue.... Placing a message like they have is BS IMHO because they are blatently blaming the issue on others when it is clearly they seem to lack the talent to seek for hidden SSID's in a secure manner like every other device does.