update: I tracked one down! It was beaconing from a small black device on top of a truck cab which looked a little like a Sirius satellite radio antenna with an extra vertical fin. It, as most of the others I’ve scanned, sent three mac addresses. No clue as to what the device was and I couldn’t make much more of it in the dim light. 🙁
What’s this? I had originally thought it was coming from onboard WiFi systems on Broward County Transit buses, or Broward parks, but it seems to have shown up in Palm Beach as well. First time i noticed a big cluster of them was near T.Y. Park, but I’ve seen lots more …. Clustered or alone.
One of these days I shall have to post my observations on retail store Wi-Fi customer tracking systems… For now though, here is what you can do about them if you have a rooted Android device.
Pry-Fi is a fun little toy for this purpose. It does a couple of things; one, it can turn background scanning on and off.
Your device always scans for networks when Wi-Fi is on but not connected by dropping a Wi-Fi probe request on each channel. This probe request contains your device’s unique hardware MAC address. This MAC address is what the tracking systems use to identify you – their business end is a number of wireless access points that allow monitoring and relay the probe requests on to a mystery server. Here’s what they look like in the wigle.net wardriving app:
Note that 78 of them replied to my probe requests!!
Pry-Fi can usually (hardware dependent) change the MAC address to fool these things into thinking they’ve never seen you before.
Best yet, it has a war mode, so when you know you’d otherwise be tracked, it can flood them with randomized probes!
It’s just kind of awesome. It won’t be able to do anything on a device without root, of course, but if it has access and the WiFi driver lets it change MAC, it can work its magic.