How can phone companies detect tethering?
Last year I called T-Mobile for some relatively minor reason and then got into a conversation about this "upgrade" I could get that would knock my bill down $20 a month, provide option X, Y and Z.<p>It sounded too good to be true so I just kept asking if I'd lose anything. I was assured, no, it's all benefit.<p>In the past if I had an internet outage at home I'd switch to to tethered phone and have no drop in speed. In fact, it was faster than work or home.<p>I recently moved and while waiting for internet installation suddenly found my tethered rate went down to .25/mpbs, whereas in the past it was up around 40mbps up and down. My phone itself reached these speeds via LTE. It became immediately apparent what I'd signed up for in my "upgrade" the year prior. I had been on some grandfathered plan that had no such restriction, and by "upgrading" sacrificed my ability to tether without moving to a One Plus plan.<p>Of course in the heat of all of this I asked myself that same question: "how does T-Mobile know?" Some of the suggestions here seem unlikely since I'm still able to get good speeds via the phone <i>simultaneously</i> while limited via computer. The MAC address thing seems compelling but I'm obviously not going to go around spoofing anything just because I got duped by my provider.<p>I've been a T-Mobile customer forever, but that kind of deception was really, really insulting.