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When reading the article I think he appears to be talking about car play/android auto connection not audio only connections. I think Bluetooth in AA and Carplay

When reading the article I think he appears to be talking about car play/android auto connection not audio only connections. I think Bluetooth in AA and Carplay is used to configure a local network between the phone and the car to transmit the images to the cars screen. I would assume that that data capability can also be used for the car to communicate with the Internet.

ezfe 4mo ago
It does produce a local Wi-Fi network but there's no evidence that it supports internet communication. That would be considered a hotspot, which not all carriers even support.
- rconti 4mo ago
  Plus it seems unlikely that the telematics module is even really related to the display screen stuff, let alone being configured to use alternate network connections to transmit data.
- dotancohen 4mo ago
  How does the carrier know that the traffic is being proxied for another device, and not e.g. requested from the phone's web browser or another app? Does the phone add a proxy header? Can it be configured to not add the header?
  - ywain 4mo ago
    Mostly by looking at packets TTL. It gets decreased by 1 by the hotspot’s NAT so if the value is something like 63 or 127 (instead of 64 or 128 which are the defaults for most platforms) then it’s almost certain the packet originated from a device behind the phone and not from the phone itself.
  - svens_ 4mo ago
    There might be multiple methods and heuristics, but one way that I have encountered was based on packet TTL. Android and Linux use 64 by default - the block could be circumvented by setting the laptop to use 65 TTL.
- zakisaad 4mo ago
  I've never understood how this can be limited in practice: surely as far as the carrier is concerned, all traffic from the mobile device is the same (unless there are identifiers on the traffic coming from hotspotted devices via the mobile device). Here in Australia we've never had any form of hotspot detection/segmentation - if you have a data plan, all data features work (across all carriers). I do recall lots of online chatter from the US though, especially years back when mobile data was more of a precious resource.
  - drtz 4mo ago
    > surely as far as the carrier is concerned, all traffic from the mobile device is the same Going on a bit of a tangent, but deep packet inspection can identify packets routed using NAT, so if the phone is operating as a typical hotspot it would be identifiable by your carrier. Carriers in the USA used to block / denylist / charge extra for tethering using this exact approach.
    - HDBaseT 4mo ago
      Deep Packet Inspection presumably requires a certificate to be installed on my device to allow my connection to be MiTM'd.
      - codebje 4mo ago
        DPI can refer to inspecting beyond just the headers, but since it's more of a marketing term than a technical one, you could also say you're "deeply inspecting" the IP headers of a packet and no-one would show up to arrest you for bad terminology. Anyway, one way to detect NAT is to observe different TTLs originating from one device. Is that deep inspection? Probably depends on who you ask. The fact that you have to track information across multiple packets counts for something, though. Off the top of my head I wouldn't really expect there to be much value in a MITM inspection of the contents of HTTP traffic for the purposes of NAT detection. You could probably come up with some scenarios in which it might be possible, but I'd content those scenarios aren't very practical. Easier to compare TTLs between packets, say, or track connections to known OS "phone home" destinations. While these just use information from the IP layer, they're stateful observations requiring comparisons across multiple packets, and that might count for something. One way to detect a shitty carrier service, though, is that they're inspecting your traffic for "good" or "bad" uses of their service, because that is a good indicator that they're not just a carrier. I call it Dickish Practices Identification, or DPI.
happyPersonR 4mo ago
Does anyone have a flow log or pcap or something from the phone showing this tho?

ezfe 4mo ago

It does produce a local Wi-Fi network but there's no evidence that it supports internet communication. That would be considered a hotspot, which not all carriers even support.

rconti 4mo ago
Plus it seems unlikely that the telematics module is even really related to the display screen stuff, let alone being configured to use alternate network connections to transmit data.
dotancohen 4mo ago
How does the carrier know that the traffic is being proxied for another device, and not e.g. requested from the phone's web browser or another app? Does the phone add a proxy header? Can it be configured to not add the header?
- ywain 4mo ago
  Mostly by looking at packets TTL. It gets decreased by 1 by the hotspot’s NAT so if the value is something like 63 or 127 (instead of 64 or 128 which are the defaults for most platforms) then it’s almost certain the packet originated from a device behind the phone and not from the phone itself.
- svens_ 4mo ago
  There might be multiple methods and heuristics, but one way that I have encountered was based on packet TTL. Android and Linux use 64 by default - the block could be circumvented by setting the laptop to use 65 TTL.
zakisaad 4mo ago
I've never understood how this can be limited in practice: surely as far as the carrier is concerned, all traffic from the mobile device is the same (unless there are identifiers on the traffic coming from hotspotted devices via the mobile device). Here in Australia we've never had any form of hotspot detection/segmentation - if you have a data plan, all data features work (across all carriers). I do recall lots of online chatter from the US though, especially years back when mobile data was more of a precious resource.
- drtz 4mo ago
  > surely as far as the carrier is concerned, all traffic from the mobile device is the same Going on a bit of a tangent, but deep packet inspection can identify packets routed using NAT, so if the phone is operating as a typical hotspot it would be identifiable by your carrier. Carriers in the USA used to block / denylist / charge extra for tethering using this exact approach.
  - HDBaseT 4mo ago
    Deep Packet Inspection presumably requires a certificate to be installed on my device to allow my connection to be MiTM'd.
    - codebje 4mo ago
      DPI can refer to inspecting beyond just the headers, but since it's more of a marketing term than a technical one, you could also say you're "deeply inspecting" the IP headers of a packet and no-one would show up to arrest you for bad terminology. Anyway, one way to detect NAT is to observe different TTLs originating from one device. Is that deep inspection? Probably depends on who you ask. The fact that you have to track information across multiple packets counts for something, though. Off the top of my head I wouldn't really expect there to be much value in a MITM inspection of the contents of HTTP traffic for the purposes of NAT detection. You could probably come up with some scenarios in which it might be possible, but I'd content those scenarios aren't very practical. Easier to compare TTLs between packets, say, or track connections to known OS "phone home" destinations. While these just use information from the IP layer, they're stateful observations requiring comparisons across multiple packets, and that might count for something. One way to detect a shitty carrier service, though, is that they're inspecting your traffic for "good" or "bad" uses of their service, because that is a good indicator that they're not just a carrier. I call it Dickish Practices Identification, or DPI.

happyPersonR 4mo ago

Does anyone have a flow log or pcap or something from the phone showing this tho?