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I have a particular problem with a potential security breach. I bought a new device today that connects to my phone via Bluetooth. Nothing strange about that.

Surprisingly when I turned Bluetooth on with my phone and set it to search for discoverable devices, it came up with 12 Bluetooth devices that I have no idea what they are.

I entered one of the MAC addresses into a MAC address database, and none of the addresses was recognised. Wondering if I had made a mistake, I put the MAC address of the mobile phone, and it correctly showed that it was made by OnePlus.

I'm somewhat concerned about why there are so many Bluetooth devices around my computer working area and would love to hear some advice on what I can do to try and discover what they are and what they are doing? I wouldn't be so concerned if their MAC addresses resolved to a legitimate manufactorer but showing not found concerns me.

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    What sort of environment are you in? From my computer desk, I'm in range of bluetooth devices in the apartment next door, the apartment above me and the one over them, many of the devices in the apartment lounge below me, and that's just the short range stuff. If I look for bluetooth devices on my computer during the day and don't see at least 30, I wonder what's wrong with it. On the other hand, if you're out in the country and the only home around for half a mile, you have reason for concern.
    – Ed Grimm
    May 4, 2019 at 16:51
  • @EdGrimm I'm in a semi-detached house with the computer room being on the detached side of the house. I'm more curious as to why the MAC addresses don't show any manufacturer when queried in the database. Surely legit devices would be properly registered? My phone is for instance.
    – Cromulent
    May 4, 2019 at 17:02
  • Cromulent - MAC addresses can be changed on many devices, so not seeing a valid one is not really an indication of anything. I always used to change mine to spell silly things (when I was younger, obviously)
    – Rory Alsop ♦
    May 8, 2019 at 18:20

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It doesn't take much to get up to 13 MAC addresses. For example, a family of four nearby with 4 cellphones, 3 laptops, a printer, a console game system, a internet router/gateway, an Alexa, a Kindle and a iPad would do it.

How many MAC addresses can you account for in your house? Laptops, desktops, cable internet modem or gateway, printers, tablets, game systems, Roku, Kindle, etc?

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My first Google hit for 'bluetooth range' indicates Bluetooth 5 has a maximum range of around 400m (over 1300 feet). This is, of course, reduced by intervening walls and devices being in low power mode and such. But Bluetooth range is a lot farther than the 50' that I was told would be its effective range when it was just a proposal.

As far as the lack of a registered manufacturer, my first guess is that they were either made by a cheap manufacturer who did not register like they should have, or they were made by a small manufacturer that didn't make it into the lookup table you used.

There are Bluetooth finder apps which would let you be able to figure out fairly easily where the Bluetooth items are. As I don't have a personal cell phone, I looked for a non-cellphone option, but there's enough apps out there it's difficult to wade through all of them, unless you have a specific target platform you're looking for.

I ended up just using a Bluetooth sniffer for my laptop. It lacks the directional sense, but by moving my laptop around and watching how the signal strength varied, I could tell they were all outside my apartment, minus my Bluetooth headset.

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