When we do defcon, Bluetooth is one of the easiest protocols to take control of. It's funny. It's also easy to spoof, easy to mess with, and generally very insecure.
I'm curious, what about Bluetooth makes it insecure? Is it that vendors create insecure implementations, like Android, or is it a human issue like connecting to things by default? I recall the Bluetooth spec being unbelievably complex and verbose, which obviously increases risk and makes it harder to audit, but it doesn't get many updates, and I don't recall seeing many issues with the spec itself. I mean it's not like it's fixing a CVE every quarter like with netty packages.
It’s too complicated. Bluetooth is complicated. It tries to do way too much, and not even the experts can implement it in a consistent fashion because different Bluetooth stacks are forced to make assumptions where the specification is unclear.
When you have a large, complex, and poorly designed specification, you’re going to get bugs. The main limiting factor has been the short range of Bluetooth preventing widespread exploitation.
Its more complex than I can talk about here in any kind of depth, but it comes down to it being a very old protocol. It has known security issues that are just not fixed as it would break backwards compatibility with a lot of devices. So the same issues that were chosen to not be fixed are still out there. You can, with very little effort, take control of just about any Bluetooth device(or partial). Or at least knock it out if commission.
I mean, just look at what happened over in ios land. Every time there is a new security issue or denial of service attack on their bluetooth stack, apple has to scramble to fix it because bluetooth is always on in their devices. Android at least has some respite by turning off bluetooth, especially on old devices that no longer receiving security updates.
Bluetooth has one of the largest network stacks. It's bigger than Wifi. This means some parts of the stack probably aren't tested and may have bugs or vulnerabilities. It has duplicate functionality in it. This opens up the possibility that flaws in how different parts interact could lead to vulnerabilities or exploits.
A number of years ago some security researchers did an analysis of the Windows and Linux stacks. They found multiple exploitable vulnerabilities in both stacks. They called their attack blue borne, but it was really a series of attacks that could be used depending on which OS you wanted to target. Some what ironically, Linux was more vulnerable because the Linux kernel implemented more of the protocol than Windows.
The Google Nearby feature thing (Google's coming version of Apple Air Tags) will require a constant background Bluetooth scanner to listen for the tags.
My opinion: that stays off. Looking for your lost phone, luggage, or ex-wife? Im not going to help you if i dont know you. Buy a new item, take better care of it.