How can phone companies detect tethering?
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The code to do that is in android here:
https://github.com/aosp-mirror/platform_frameworks_base/blob...
There is a setting you can set to disable it and make the provider treat all traffic as if it is non-tethered.
adb shell settings put global tether_dun_required 0
net.tethering.noprovisioning
consumed here:
https://android.googlesource.com/platform/frameworks/opt/tel...
"Hey, your service doesn't work even though I'm sending those packets from my phone. Give me my money back".
They don't need to prove it and they have no obligation to give you your money back, either. Be careful.
Except it's Java ... too much bloat to go through.
Their networks are often provisioned under the assumption of super bursty traffic, where not all phones will be pulling at throughputs all the time. Laptop users will tend to use high throughput more consistently, and so be bad for their business model on the cost side.
The first 2 or 3 google phones I had let me turn on tethering with no problems despite it not being in my contract and somewhere around the pixel 2 it stopped working. So it seems like an intentional change on their part, and likely one that Apple also enforces. To change the flags mentioned previously you also need root, so it provides quite a speed bump for folks trying to use tethering despite it not being in their contracts.
Phone manufacturers alter from there per carrier demands. Phone manufacturers us Android because it's free.
It's brilliant on Google's end.
Perfect example, is WiFi calling. That was available on Android forever, but only T-Mobile didn't restrict it. ATT and Verizon had it disabled because of how profits are calculated on cell sites. There's a whole per minute, text, and data calculation that shows money flow. T-Mobile allowed WiFi calling way back when because the network was a dwarf to the big carriers. And then apple caught up like normal and acted like they invented it, but don't even get me started on apple.
I am a little confused, this creates a new interface named `rndis0` how does the carrier know it's tethered? Because of the new MAC address?
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.
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.
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.
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 simultaneously 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.
I've been a T-Mobile customer forever, but that kind of deception was really, really insulting.
The iOS app I “wrote” is up on GitHub: https://github.com/nneonneo/socks5-ios. It’s really barebones; I knocked it together in less than an hour since I rather desperately wanted a good internet connection at the time :)
But, hey, if you want to see some random person's SOCKS code bodged up with some extra hacky bits from me, here you go: https://gist.github.com/nneonneo/fc770965944a4640e2aef34e0f8...
If you want to use PAC, set the "automatic proxy URL" to http://172.20.10.1/wpad.dat when using this as a tethering proxy (yes, iOS lets you bind port 80 without root - your app just needs to be running).
Our billing, IMO, is very not up-front about what our limits on tethered/not are. Generally, it hasn't mattered. Whatever our limits are, we're not hitting them.
And it's annoying AF; there is no reason for a carrier to give a crap about tethered/not. Limit my bandwidth, cap the amount I can send, sure — I completely understand not wanting a customer dragging down the network —, but what does it matter what device generated the bits?
Put yourself in their shoes, and you'll appreciate their reasons.
I was recently force to pay for a higher plan specifically to unlock tethering, which is important to us for backup, since we're in the hills on a crappy ADSL connection.
Their reason is that it allows them to increase revenue.
Just because they are both packets over the network, they are different use cases and present a feature which can be charged for.
If you don’t like it, switch to a different provider. If there isn’t one that meets this need, maybe there’s a market opening. If the market is anti-competitive and exploiting that and colluding to shut down this feature, complain to the FCC. If the FCC dismisses your valid complaint for political reasons, vote out the party which put them there. If you don’t have the votes to get the people in power to care about this issue and regulate against the monopoly which is colluding to overcharge for it, then deploy a few thousand bots to sow dissent on Twitter and... no wait, don’t do that last one.
Charging people for different use case while the product is literally the same is one the most anti consumer things I can think about it, no idea why you think it's okay.
Imagine a eletricity bill that had different prices if your vacumm cleaner was being used on the living room rather than say, a bedroom, I see it as simply absurd.
Most of the packages they sell are based not on the cost of your specific consumption (which is way more complex than peak bandwidth or total transfer), but the cost of typical consumption given some restrictions (e.g. the aforementioned bandwidth or total volume cap).
If you bunch tethered and non-tethered traffic together, the average non-tethered user will have to pay more, and the average tethered user will have to pay less, than with the two usages split (assuming the same total profit).
Thus, you would lose the "cheap" non-tethering customers to competitors who do differentiate, while the expensive tethering customers would come to you.
I bought a $75/month “unlimited” plan (soft cap is 50GB before throttling according to the sales rep) and that price tag includes any taxes or fees in my local jurisdiction. It is $70/month with autopay turned on, because you get a $5/month discount. The hotspot would suck if I used it, but I don’t, and FaceTime Audio works out of the box, no setup process, which was what I wanted to hear.
Wireless is different. There is only so much bandwidth that you can have over a given frequency, only certain frequencies are available to each carrier, and only certain frequencies are conducive to cellular transmissions. For instance for years T-mobile has horrible reception indoors because of the spectrum they had.
https://www.t-mobile.com/offers/mydatausage
It looks like you’ve used 48GB or more of data overall in this bill cycle. After 50GB, you still get unlimited LTE data but may at times notice reduced speeds in areas with network congestion.
In the vast majority of times and places, you will notice little if any difference. In the small number of times or locations where there’s network congestion, you may notice reduced data speeds. This experience is due to our data prioritization practice, which prioritizes customers who use more than 50GB of data in a single bill cycle after other customers. This practice helps to optimize overall network performance and maintain a quality service experience for as many customers as possible. Your data usage resets at the beginning of your next billing cycle, so this practice will only apply until that time.
Stock android and iOS will use the tethering APN under the hood. LineageOS doesn't.
I'm presently tethered to a tmo phone on their cheapest unlimited data plan and see 20mbit+
Here's a random howto change ttl for Ubuntu and windows: https://askubuntu.com/questions/667096/how-to-change-the-def...
Btw, an interesting article on the effectiveness of TTL for fingerprinting: https://www.howtogeek.com/104337/hacker-geek-os-fingerprinti...
Did you try calling T-Mobile? I would be curious if they could confirm it was in fact throttling tethered devices and if they could explain and maybe correct the behavior?
I tried to dispute the bill and they sent it to collections. Also, during signup they ran a hard credit check explicitly against my permission. One person vs BigCo doesn’t always work out.
It worked so well (for the heavy phone consumers) that the company tried its best to buy those contracts back / move those folks on a more profitable plan.
AFAIK this wouldn't work because MAC addresses don't get forwarded to the next network segment. On android, the phone acts as a router (with its own DHCP server assigning devices a local IP address), so I doubt that information is getting passed on.
>Inspecting the network packets for their TTL (time to live)
>TCP/IP Stack Fingerprinting
>Looking at the Destination IP/URL
Probably works, but I'd imagine it's pretty easy to bypass by proxying your connection through the phone.
I'm sure that if there's enough demand for it, someone would make an app. A simple SOCKS5/stunnel server with a few buttons shouldn't be hard to make.
>and there is still a possibility to detect PC by analyzing unencrypted DNS queries to MS domains for telemetry servers.
This would really only be an issue if you don't have VPN killswitch set up on the tethered devices. Even if this can't be prevented, disconnecting phones because they made a connection to MSFT telemetry servers can be easily turned into a DoS vector. Want to mess with someone's internet? Put a bunch of img/script tags to MSFT telemetry servers on your site.
I needed to tether on train rides a few times a year, which was really not worth paying for the service. Nowadays I can do it without an exorbitant extra charge (aside from the extra data that tethering guzzles), so there's no need for it.
Finally! I was scrolling down the comments, starting to think nobody on HN knew networking enough to notice this.
MAC addresses never "leave" the local network segment, so can't be used for tracking tethering unless the phone has code to forward this info on. But, at that point, the MAC address isn't really needed anymore ;)
Whereas with data, there is no limit intrinsic to tethering vs in-phone.
More to the point, in practice, people can easily use as much data in-phone as on a laptop, due to streaming video. Think, for example, of someone streaming music via YouTube for hours on end.
It's why I like Google Fi. I don't have any of these arguments. I'm just fully metered and there aren't any restrictions.
There are actually several tricks to make video streaming efficient for phones. The top sites are aggressively throttled [1]. This is harder to do for laptops, where users are typically connecting to corporate VPNs and stuff.
[1] https://www.bloomberg.com/news/articles/2018-09-04/youtube-a...
And anyone who uses a VPN can get themselves limited, just like they were using a laptop, because the carrier thinks you're trying to hide something from them.
Here's a different analogy that might work better: I can shop at Costco as much as I want, and I can even buy things for other people, but I cannot literally give my Costco card to someone else and let them shop at the store on their own.
People also deal with various data caps when tethering, they just now also deal with an extra bill for a service provided by their phone not the phone company.
it was based on the same argument that multiple devices would be used by multiple people and hence create more traffic.
i don't know if this was common in the US, but it certainly was in some countries in europe.
Tethering is problematic in many ways with devices that don't expect to be metered. A Windows PC or Mac will sop up data sitting idle at a prodigious rate.
For every informed consumer who understands that, there are 8 who are going to go crazy when they end up with a wacky bill.
Thankfully, Windows finally offers a "This is a metered connection" option. Do you know how to get the equivalent functionality on a Mac? I've looked, but can't figure it out.
The fine-grained control is nice but still seems like a glaring omission that the Mac still isn’t “tethering-aware” with regard to conserving data — especially since it’s so seamless to connect to an iPhone that shares the same iCloud account.
Its like if you subscribe to netflix .. but if you want to share it with 4 family members, then get a family plan. You can simultaneously consume multiple streams of content.
Tethering allows you to share the internet connection with other people, as well as your other devices - which is essentially you consuming multiple streams of internet data simultaneously.
To me, metering a "tethered" connection differently than the phone making the same requests is just as disgusting as an ISP charging you because you have a different number of computers connected to the internet on your residential connection. Or charging you more because you went to a streaming site. It's a blatant violation of net neutrality.
If a cell phone company can't fulfill their advertised service of x mbit down / y mbit up, they shouldn't be offering it. Anything else is false advertising.
This issue constantly comes up with keeping the internet free and open. Take the following:
The customer pays for their connection, say 10mbps over Verizon's network. Under a free and open internet, the customer is allowed to use that 10mbps that they PAID for in whatever damn way they please.
Why should I be subject to Verizon's idea of what my connection should be used for? Congestion happens, but a properly designed network means that the pipes are mostly free and available under normal circumstances to all customers for all the bandwidth they paid for. Doesn't matter how many devices I use on the other side of that connection, I bought 10mbps and I should be able to use that 10mbps the way I want.
This is price gouging. Plain and simple.
That's typically not what happens with commercial ISPs. You pay for access to some parts of the Internet with asymmetrical speeds (often 20Mbit to 1) and most times without even a publicly routable IP address ("for your security").
Even if you pay that commercial ISP for higher speeds, you can read in the contract that they're actually not guaranteed and that anyway people exceeding "reasonable limits" (usually not defined with actual numbers) will have access shut off.
So sure you can do that on a non-profit and/or professional ISP because those will be explicit in what service is brought to you for what prices (without surprises) and they will usually stay out of your way when it comes to how you use the network (public IP, no port blocking, no priority for Youtube traffic over important mail, etc).
So if you find this situation as revolting as i do, welcome to the fight against the telecoms industry! We can do better, cheaper, and more intimate Internet.
Paying for usage sort of makes sense, but paying for a license to share with other people? That's outrageous.
Imagine if you had to pay an extra license on your water bills for sharing water with your guests..
The cultural industry from your first example has been unjustly profiting from artists and the public alike for decades.
Now ISPs need to apply this model to survive because we don't pay for bandwidth usage or for guaranteed bandwidth. We pay for a mirage of advertised 28Mbit/s, 100Mbit/s, or even 1Gbit/s nowadays.. the cost of which bandwidth is actually shared among many clients.
So it's specifically because of their own marketing lies that ISPs now need to find ways to restrict users from sharing their access. Good luck with that!
In the meantime, we'll keep on building our own self-organized non-profit ISPs (such as NYCMesh or guifi.net) to overthrow their rule.
Paying for USAGE is disgusting. The way a network works, is that besides upkeep which is a small percentage of TCO, upfront cost scales with total bandwidth, not total number of packets one needs to move across a set of links.
Meaning if the ISP buys enough network equipment for 100 users to each have 10mbps of available bandwidth, they no longer have costs besides upkeep (maintenance, support, and replacing broken hardware). This is a SMALL percentage of upfront buildout costs. This large lump sum in the beginning has the potential to deliver the same amount of bandwidth ad infinitum.
Charging users for USAGE is DISGUSTING and is literally not fair.
Price gouging.
Plain and simple.
In the context of a typical end-user paying a non-profit ISP, yes. We share infrastructure costs and that's about it.
The problem is commercial ISPs only follow the money so you have the recurring cost of greedy shareholders to take into account in your equation. And that usually leads to not respecting net neutrality (as was the original subject of this thread).
So if you are in control of your own infra, price for access should be in the range of 1-20€/month. If you do xDSL, it has to be (a lot) more expensive (+15-25€/line/month).. as long as you're small. When you're big enough you can do local-loop unbundling and be back on the first price-range.
> Charging users for USAGE is DISGUSTING and is literally not fair.
Depends. For typical end-users, it's not a good model (you want a fixed price). But for associations, hosting coops, companies.. That's the usual approach for guaranteed bandwidth billing: https://en.wikipedia.org/wiki/Percentile#Applications
That's a mechanism to make sure your friends and your small neighborhood association don't have bleed themselves to pay for the seedbox i want to setup in my garage :)
Without firsthand experience, it's difficult to explain to someone that once I configure an access layer switch with 48 1gbps ports on it, and 4 10gbps SPF+ uplinks, it only costs me the price of electricity and physical storage to move 1 packet over it, or an infinite number of packets over it.
My problem with that is that once the pipe is installed and working, it only costs maintenance. I'm not sure what you are trying to say with your seedbox example.
This really isn't true, as you do have to pay someone to sit somewhere nearby the switch in case it goes down. And you have to maintain a space indoors for the switch so that it doesn't get wet. Such space has to be built on land that you own or lease, and you can't just buy a wiring closet-sized piece of land. You also will have to eventually replace the switch, as it will fail after a certain period of time.
There are recurring costs to all of these things, and it absolutely costs more to send an infinite number of packets over the switch. In fact, you can only send so many packets over the switch before it fails, because bandwidth and packet size are limited.
You'll also find that if you're selling bandwidth on this switch you'll need to pay people to administer and enforce contracts, and you'll need a building for those people, and you'll probably want to market your switching service so people know they can buy bandwidth on this switch from you.
It's pretty dismissive to call all that "maintenance" as if it's a paltry sum. In fact I would argue that paying the company to maintain the network is the bulk of what you're paying for here, and it's a lot more complicated than just plugging some wires in and calling it a day.
Not my intention, sorry. Per-packet pricing would be ridiculous indeed.
> not sure what you are trying to say with your seedbox example.
"Per pipe size" pricing doesn't mean you only have maintenance costs. Because it's technically unfeasible to guarantee "pipe size" bandwidth to all routes on the internet to all your clients. So if i keep "my" pipe filled, you may have to add new cables/switches or maybe upgrade some transit plan.
So i can understand that with a 10Gbit/s uplink you may never reach these limits because your network is already oversized for your needs. But many people (even actual ISPs) don't have 10Gbit/s uplinks. Or at least not 10Gbit/s of transit (although they may have 1-10Gbit/s peering links with other local entities).
Yes I agree. But if I pay an ISP for a 10mbps link, I should be able to get 10mbps to their NOC at all times, and then each ISP would be able to vary prices based on peer connectivity. This is where competition would strengthen the internet backbone.
This isn't really true for wired networks, and it's extremely untrue for wireless networks. There is only so much total aggregate bandwidth available in a given area's spectrum allocation. If every device at a given base station was downloading as fast as it could, performance for all users would collapse. Wireless ISPs need to get users to limit their usage. In the past they did this by charging the byte. This confused users, and got them angry, so now they've migrated to "unlimited" plans where you effectively pre-pay for (say) 30GB per month and then get slower downloads beyond that. They've also added tricks on top of that to make it harder to use a lot of bandwidth. This includes making it harder to tether, and throttling music/video streaming services.
Oh.. and I have an ad blocker that saves a ton of network
You get a Netflix family plan if you want four people to simultaneously and independently connect to Netflix, each consuming their own stream. You don't need a family plan if you plug Netflix to your TV and invite three other people to watch a movie together with you.
Tethering is like the latter case. Your phone is still a single device consuming a single Internet connection. The concept of "multiple streams of internet data" you used exists only because phone companies violate net neutrality, refusing to become dumb data pipes they should be.
The sharing with other people component may be specific to the service and with Netflix probably outweighs users actually watching 2 streams on 2 devices whereas with tethering I think it's more likely sharing a connection with another device the subscriber owns like work PC when traveling or a media device on the go like tablet or computer.
the tethered devices use the same "gas tank" and would have to be directly connected at all times for that to work.
so maybe
"you get unlimited diesel for this car, but you'll have to pay extra if you want to charge your phone or laptop from the electricity generated from our diesel"
If you want the ability to give apples to friends to eat, then it will costs extra.
Maybe have an app or webpage where you push a button and some contracted delivery person brings you an apple.
I'm tethered right now to Sprint which really doesn't appear to give a shit. Their network is encapsulated to all hell since it's ipv6-only so I recommend decreasing MTU's when connecting to it (something like 1320 seems to work or sites like duckduckgo get blackholed). Sprint sucks unless you're line of sight to a band 41 tower and/or have a HPUA device.
T-Mobile detects tethering a matter of ways. I use a Moto E LTE 2015 (surnia) as a dedicated modem phone for them. I modified lineageOS 14.1 for my specific use case (namely just to add TTL as a target in the kernel for iptables). I also use Network Signal Guru to lock it to the meatiest band in my area (band 4 broadcasts at 20mhz)
The magical iptables option to pass is: iptables -t mangle -A POSTROUTING -j TTL --ttl-set 65
They detect certain services like playstation network, so you have to VPN that so it isn't counted. I disable ipv6 on the t-mobile APN too as an added layer of protection. Average use is around 250-300gb/mo, this is rural so it's unlikely it causes any quality of service issues (and I don't end up subject to deprioritization issues after 50GB)
EDIT: Should also mention at least T-Mobile used to do DPI on the User Agent sent by browser years ago. They don't appear to do that anymore (widespread HTTPS made that pretty useless). Back then I used to just get around port blocking by ramming my traffic through SSH dynamic port forwarding on port 143, normally used for IMAP. This was for T-Zones service level in the early 2000's.
Oh and for AT&T in the later 2000's I used to buy import phones that weren't in their system and use them on the non-smartphone unlimited plan until they got wise to that.
EDIT2: If you find ethics of this questionable, can't be hassled to figure this stuff out, and/or still want to use LTE unlimited where money is not a concern there's plans for that: https://unlimitedville.com/
I tried a lot of ways to get around that (most of what you mentioned, tweaking my hops and what not) and never made any progress so I assumed it was at the network level and I'd have no control.
If you live in a populated city or need to go through an airport with a phone subject to deprio you're going to have a bad time with speeds.
If you're like me and live on a mountain surrounded by trees with a line of sight to the tower down the hill, deprio isn't going to matter.
"unlimited 4G / LTE wifi data and a mobile hotspot from Sprint", is meh for $500.
Consider this: Buy a unlocked Fi moto X4 from best buy for like $200, do the Sprint BYOD deal with a Google Voice number ($3 to unlock number for porting), this will give you $4/mo 'unlimited' service for a year. Slickdeals has a long in-depth thread on the full details of this arrangement.
I will also point out that a lower WAN MTU will cause forwarded (and only forwarded) outgoing connections to fail if the phone's firewall rules aren't properly configured to adjust TCP MSS! Pings will work, sites will connect, but you'll get no data back. This can seem awfully like some kind of active interference, when it's just a passive network problem.
These 22gb then deprioritized "tablet" plans are available for $35/mo. It requires generating an iPad or similar IMEI to register. I've tethered and used video chat/games/VPN and had no issues.
If they're going to offer "unlimited data", then they should give exactly that. If you want to share it with the whole neighborhood, that's your business. If that's a technical problem for them, then they shouldn't be offering "unlimited data" in the first place.
https://www.ofcom.org.uk/about-ofcom/latest/bulletins/compet...
One telco customer did not have tethering limitations in their customer contract agreements, so this one end users customer bought a number of devices, and then would resell internet service in local rural areas using his devices as backhaul. This one customer and his dozens of "ISP" devices were doing gigabytes and gigabytes of data per month, using approximately 80% of this whole carrier's data capacity.
I called them up, because I wouldn't mind paying a small amount extra every month to have that ability. However, they told me that they actually couldn't provide it with my phone even if I paid, because they didn't support my phone (Pixel). Then they tried to upsell me on "compatible phones"...
I used this phone as a hotspot with my previous provider, so I know it can be a hotspot. But I don't know much about the technical side of this. Does anyone know if what they're saying is plausible? (Ie, they can't offer it for my specific phone)
I briefly tried a few apps for this purpose, but none of them worked.
I used to use Vodafone NL, and apparently they used a SIM provider ID that matched Verizon or something in the US, so my phone (Pixel 1 at the time) would ask Verizon if this SIM was allowed to use tethering, and of course it said no. Part of the reason I moved carriers, also the new one has unlimited data which is better anyhow.
Vodafone had no idea what was going on, although they did try. Eventually they just said they couldn't help.
Anyway, maybe something similar going on for you.
Of course, it's only in some states (like Maryland) where recording conversations without permission is illegal, but that's enough.
Google already has this, with google voice, press 4 during a call to start recording it. (only on originally incoming calls.)
One: most laws do not require permission or consent per say, simply having the feature also pimp out a recording that says "Call is now being recorded" like the google voice feature already does is enough to keep it legal.
Two: "Made explicitly for illegal uses" is a wide stretch for a call recording feature.
[0]: http://foxfi.com/
edit: Here's their page from 2012, they were marketing it as "Hybrid Calling" https://web.archive.org/web/20120103104716/http://republicwi...
The cell data you pay for is your cell data usage, you (of course) don't pay them for your wifi data usage.
(Disclaimer: Happy customer and investor with Ting/Tucows since 2012)
https://help.ting.com/hc/en-us/articles/205422068-Tethering-...
Do be aware though that I haven't found a generic way to bypass TTL detection, as most solutions use the "mangle" table in iptables, which requires a kernel module on Android. Unfortunately, this is not generic and would be per-kernel.
This is another excellent question from the earlier days of stackexchange that are all now "offtopic". Its sad to see it consistently lose informative questions. Stackexchange's policy shift toward marking any slightly general question as offtopic is a sad state of affairs.
netsh int ipv4 set glob defaultcurhoplimit=29
netsh int ipv6 set glob defaultcurhoplimit=29
Alternative to a VPN as a proxy you can install Termux on Android to install and run a sockS5 proxy.
I have to carry two devices because of this. :(
Also in this list: Apple allowing video players to disable seeking in ads. It’s my hardware, fuckers.
No, it's not. This has been shown time and again.
The problem discussed upthread is on the application layer - you not being able to run arbitrary code on your own device because companies prefer to please one another rather than their customers.
In a market with competition device manufacturers would be fighting over adding features like anonymous teathering for their customers, and phone companies would be charging for data use, and with enough competition that use-per-byte would become dirt cheap quickly.
note that it's a semi-untethered jailbreak so you have to re-jailbreak every time you restart, but that basically comes down to opening an app and pressing a button.
The product can still be good and useful even if the product managers are carrier-bootlicking shitheads who place a third party’s interest above that of their actual paying customers.
You do not own the device, Apple does. The device is Apple's slave. It obeys its master and not you.
The law even backs up this, the Digital Millennium Copyright Act forbids you from doing what you want with it. If you don't live in the US, don't worry your home is probably a party to WIPO and anti-circumvention is illegal there too.
It is not your hardware. Your "ownership" is abrogated by law.
What reasoning would they have for that? It's an Android stackexchange after all.
However, one app would make calls out with a User Agent that looked like IE6 which caused the network to disconnect my data and require me to phone up to get it unblocked.
I'm sure my custom ROMs played some games to disguise the traffic, but at least on AT&T it seemed to work without a hitch.
The thing is, my plan did not require the extra fee when I signed up, and so that had been grandfathered in.
When the telco does this, you can switch to another one, but you cannot port your number. This would be like the postal service owning your street address. If they took a dislike to you, they could prevent you from using the address!
I'm not sure there is much else with which the network can tell is there?
As to why they’re doing that I have no idea, I guess they want to see your traffic in the clear and so block most VPN protocols (though you should be able to get a TLS-based VPN working over port 443 as it’ll look like standard HTTPS).
You can also use some simple ssh forwarding from the phone (like SOCKS5) even if VPN is not available. ISP won't be able to differentiate that from other traffic.
Q: How can phone companies detect tethering?
A: by working with Google and Apple to inject code in android and IOS to serve that purpose.