https://discuss.grapheneos.org/d/7710-changing-imei/8

A phone doesnt need a sim to connect to the network towers. Sim is only for billing. The network can see your imei and triangulate your location as long as your radio is on.

I have read this on https://discuss.grapheneos.org/d/7710-changing-imei/8, but I’m bit confused. Does this mean our IMEI is identified by cell tower as long as the airplane mode is off? What exact setting is “Radio” referring to?

thanks a lot

thanks @rowinxavier@lemmy.world and @9tr6gyp3@lemmy.world

Short answer: Yes The network can see your IMEI and triangulate your location even though no SIM is installed. and theoretically with airplane mode off no radio is on

  • rowinxavier@lemmy.worldEnglish
    45·
    2 days ago

    Put simply the radio broadcasts a sort of hello message to the tower so the tower knows where to listen (this is about signal direction or beam shaping, but imagine the eye of Sauron swiveling to see Frodo). This includes the identifier of the handset, the IMEI number, so that the tower can keep track of who is who. The second step of getting connected to the network is done with the details inside the SIM card, specifically the IMSI number.

    If your phone has no SIM card you can still make an emergency call. You can also have an eSIM which is a software version of the SIM card. In both cases you can bypass the SIM and get connected.

    If you turn airplane mode on the radio is powered off in theory, but this is not absolutely guaranteed. It should be off, the system will report it is off, but there are fringe cases where it may still be very slightly active, usually from malware or similar things.

    So no SIM means no IMSI, but the radio itself has the IMEI and that handset is hard coded to that identifier. If the radio powers on it will broadcast the IMEI to negotiate connection with or without the SIM and IMSI.

    • FrostyCaveman@lemm.eeEnglish
      1·
      1 day ago

      That seems like the tower must have to keep track of a hell of a lot of beam direction info. Damn

      • rowinxavier@lemmy.worldEnglish
        1·
        19 hours ago

        Yeah, it is a fairly large dataset depending on the tower location. For example, in an inner city locale you may have hundreds of devices on a single passenger train going past a local tower. These transient handsets used to cause a massive issue with drop outs and loss of signal as they would acquire and then drop service from a given tower. Nowadays we have solutions for this which centre around shaped beams along the direction of travel with communication between towers to ignore handsets which are moving along a travel corridor.

        To make that clearer, imagine the overhead train line has passengers moving along and under the train line people are walking on the street. The various towers which are along the train line will pass information about which handsets are moving and which are local so the local towers can handle local handsets and specific towers above can handle the train customers. This keeps the lower towers from changing their directionality and dropping calls and data confections, but also allows the train handsets to have reasonable connection to the network.

        Another interesting case is what used to happen at the edge of the range for a tower. The whole tower could modulate its power so it could reach a far off handset if nobody else was around, extending the effective range. This unfortunately meant that if someone came closer to the tower it would have to lower its power to not harm the handset and the person far away would lose signal.

        Nowadays the power level can be handled per handset. Each handset gets a small portion of a second, actually a small handful of parts of a second, and the power of the tower is adjusted to reach them at their required level for their time slots. If someone comes online close to the tower you may have competition for the time of the tower and thus lower speeds but the power will still match your handset independently of the rest. Very cool technology, way better than what it was with GSM, and also much more secure.

  • Laser@feddit.orgEnglish
    10·
    2 days ago

    Radio here refers to your mobile (non-wifi) wireless connection, though technically, Wi-Fi is also radio and can be used for triangulation purposes by access points. Technically speaking, any communications method that uses electromagnetic waves is radio, regardless of modulation and data encoding.

    Does this mean our IMEI is identified by cell tower as long as the airplane mode is off?

    The IMEI is how the cell tower differentiates the individual network participants. It can be compared to a MAC address.

    • happeningtofry99158@lemmy.worldOPEnglish
      23·
      2 days ago

      Radio here refers to your mobile (non-wifi) wireless connection, though technically, Wi-Fi is also radio and can be used for triangulation purposes by access points. Technically speaking, any communications method that uses electromagnetic waves is radio, regardless of modulation and data encoding.

      I can use WIFI with Airplane mode, is my IMEI being transferred to any place in this situation?

      The IMEI is how the cell tower differentiates the individual network participants. It can be compared to a MAC address.

      Can you elaborate how it is compared with MAC? What might happen to how cell tower compares IMEI and MAC when I spoof MAC?

      • Laser@feddit.orgEnglish
        4·
        2 days ago

        I can use WIFI with Airplane mode, is my IMEI being transferred to any place in this situation?

        No

        Can you elaborate how it is compared with MAC? What might happen to how cell tower compares IMEI and MAC when I spoof MAC?

        A cell tower doesn’t care about your MAC. In fact you can have devices without a MAC in a mobile network (like dumbphones). However, a malicious entity might be able to correlate these two with a setup where he controls both cellular and Wi-Fi equipment.

  • whyNotSquirrel@sh.itjust.worksEnglish
    6·
    2 days ago

    In some countries you still can call emergency services without SIM cards, so your phone can still reach the network for this purpose

    Radio refers to the network, so yes for it to not connect only airplane mode works in my knowledge (you can activate WiFi after)

  • 9point6@lemmy.worldEnglish
    4·
    2 days ago

    The radios are the parts of your phone that communicate wirelessly. Most phones will only turn the cell radio off entirely during airplane mode, disabling mobile data does not typically turn that radio off.

    Airplane mode should turn everything off (unless you re-enable things like WiFi, but that should still keep the cell radio off)

    • happeningtofry99158@lemmy.worldOPEnglish
      12·
      2 days ago

      Airplane mode should turn everything off (unless you re-enable things like WiFi, but that should still keep the cell radio off)

      I can use WIFI with Airplane mode, is my IMEI being transferred to any place in this situation?

      • 9point6@lemmy.worldEnglish
        1·
        2 days ago

        It shouldn’t be, no. But one of the big problems with phones currently is that the radio firmware is almost always a closed-source binary blob.

        Airplane mode is probably better understood as the OS asking the radio nicely to not attempt to communicate with the outside world. The antenna is still there able to receive signals, and the radio technically doesn’t have to listen to the OS if it doesn’t want to.

        It’s incredibly unlikely (researchers look for this kind of thing), so make sure your tin foil is on tight, but not impossible that a radio could store cell tower identifiers it has seen whilst on airplane mode and do something with them when it is allowed to communicate again. There’s also the possibility there’s some secret signal that can be sent to force a phone in airplane mode to respond.

        Unless you’re up to some Edward Snowdon level stuff though, even if that last one exists, it’s probably not being used on you.

  • notabot@piefed.socialEnglish
    4·
    2 days ago

    Yes, the IMEI uniquly identifies the phone itself, so if the GSM radio is on, the network can monitor it’s approximate location.

    There’s a couple of caveats: IMEI cloning is possible, but unlikely, and he accuracy of the triangulation will depend on a lot of factors including how far apart the towers are and what sort of obstructions there are between you and the towers. My understanding is that it is done by comparing your signal strength at each of the towers as a proxy for distance. If there’s a large obstruction that reduces your signal to a tower it could throw those measurements off. They’ll know you’re in the area, but not exactly where.

  • 9tr6gyp3@lemmy.worldEnglish
    62·
    2 days ago

    Radio is referring to the proprietary piece of hardware that is in every cell phone that handles the physical portion of transmitting radio waves for wireless connectivity. This piece of hardware generally handles LTE/5G, wifi, and bluetooth.

    Your IMEI is the identifier that is burned into that hardware, which uniquely lets the carriers determine if your device can authenticate on their networks.

    You can turn off the radio by disabling your cellular network or turning on airplane mode on your phone. You will temporarily lose access to your cellular network until you turn it back on.

    Newer devices don’t require SIM cards to connect. They have eSIM cards that can be used. You still need one or the other to connect to a cellular network.