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Comment by tppiotrowski | Hacker News Reader

> Location: Your precise physical location in the store (with your consent), including when you enter and leave a store (Kroger app, GPS, and Bluetooth beacons inside stores)

Can someone comment on how a store can identify my Bluetooth address if I never pair with anything in the store? Do apps have access to the Bluetooth MAC? If the app is not running, can the store still identify you using Bluetooth? Is there some advertising database that contains MAC addresses tied to identities?

If you're on the store Wifi and open the app, I'm guessing the store can record the MAC address and look for it even if you're not connected but scanning.

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There are a number of methods that "work" to varying degrees. For bluetooth, stores can install ble beacons that a phone app can detect (if it has permission) and then get a rough estimate of the general area in the store you are in.

For wifi, stores can detect your phone's probe requests to estimate your location. If you are not associated to the store's wifi network your probe requests will use a randomized mac address (at least with ios and pixel devices). This means they probably won't be able to identify you as a new vs returning customer.

Stores also use cameras to track path traversal throughout a store. These paths are difficult to tie to an actual identity so are generally used in aggregate and not for more targeted marketing.

If you have bluetooth on, beacons can try to connect and track your movement throughout the store. With Apple and Google both instituting rolling bluetooth mac addresses, this doesn't persist across the whole visit to the store, but will still let them see how long people stand in front of the cookies or how quickly they pass by the eggs.

It's also probably not that hard to recognize a freshly rolled over mac address as belonging to the same device as the previous address.

It's not.

1) The MAC that you saw entering the store and standing in front of the eggs vanishes suddenly.

2) A new MAC appears suddenly in front of the eggs.

3) Therefore, new MAC is probably the same device as old MAC

Most folks just click 'accept' on any permissions dialog pop when using an app. They don't care what 'discover local network' or 'use bluetooth' means.

So, for many, it's just installing the app and it's collecting/signaling with their permission. Independently, your phone transmits on bluetooth frequencies with a MAC, and that MAC is unique to your phone, so while it might not be linked back to you by a specific app, other apps might report (say, they play bluetooth audio or something), and get indexed and correlated elsewhere.

https://www.skyhook.com check out something like this for more info...

7-Eleven has this feature. I remember poking around their American iPhone app and they had libraries for this functionality.

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