Wi-Fi Sniffing Lets Researchers Build Graph of Offline Social Networks

angry tapir writes "The probe requests emitted by a smartphone as it seeks a Wi-Fi network to connect reveal the device's manufacturer thanks to its MAC address. This can offer some information about a crowd of people by looking at the breakdown by device brand. However, because some OSes include a preferred network list (PNL) in their probes, it may be possible to use Wi-Fi sniffing to infer even more information about a group of people by looking for common SSIDs, and potentially mapping them to known network locations (PDF). A group of Italian researchers has been looking at ways to use the information in probe requests to analyze the social connections of crowds." The idea being that if you share preferred networks (especially ones only seen infrequently) you are more likely to be socially connected.

Comments

McDonalds WiFi SSID

[EMG at MU]

Let me guess, if you share that preferred network you might be part of the overweight social circle?

Do strip joints have WiFi? That would be another interesting social circle. Now you can know who in the office likes to kick back and watch the talent.

Yeah right

[Fnord666]

Like anyone is using their real MAC address anyway.

Illegal

[Solandri]

Didn't you get the memo? The courts think sniffing open wifi networks is a violation of wiretap laws.

snoopin in places I didn't know I had places

[Iamthecheese]

These scurvy snoops be too interested in things that don't concern them. Must I hide not only me mac, computer name, browser type, and personal information but local network addresses as well? I'm really tired o' puttin' up new curtains. Me treasure maps will be well hid no matter how I have to do it but I'm wanting to put me wooden leg up some CEO asses.

Hah

[Richy_T]

This is why I keep my phone under my tinfoil hat.

Another example of data "leakage"

[WuphonsReach]

Eh, the better question is "why does your computer leak data other then the MAC address"? Which is exactly what the PNL (preferred network list) is doing.

Sure, it might save battery life, but information leakage like that should be off by default.

Re:Another example of data "leakage"

[jrumney]

Because some people configure their access points to not broadcast the SSID in the misguided belief that they can add a layer of security by doing that, devices will actively try to connect to networks that they cannot see. So anyone anywhere can see your device periodically trying to connect to every network that it is configured to connect to automatically. This doesn't save battery life, if anything it uses more than sitting passively listening for known networks would, but the idiocy of hidden SSIDs is widespread enough that it is necessary for WiFi to just work for mobile devices.

Re:Another example of data "leakage"

[semi-extrinsic]

According to this, Android only broadcasts a partial PNL: it sorts network into those you added from the scanning list and those you have configured manually. It assumes that all SSIDs configured manually are hidden ones, for which it must broadcast the PNLs. So if you have never added a network manually on your Android phone, the PNL broadcast list is empty.