AT&T knew you were tethering all along, and now they're doing something about it


Many people like to make use of the data plans from their carriers on more devices than their smartphones. The process by which they do this, called tethering, allows them to use their phone's data plan to access the internet from their laptops or other mobile devices. Although users enjoy this capability, carriers do not like people tethering because it usually results in more data use and more taxing of their networks. 

People who want to tether their phones for free usually rationalize that because they have an unlimited data plan, they should be able to use as much data as they want. Carriers don't share the same sentiment. They usually attempt to charge users for unlimited data and restrict their device's tethering capabilities. In order to unlock those capabilities, users are supposed to pay the carriers more for a "tethering plan." 

Unsurprisingly, adept users have found ways to circumvent these charges with both iPhones and Android devices. Most users feel safe tethering without the carrier's permission; after all, they are paying for unlimited data plans. Plus, the data is all the same to the carrier, right? There is no way they would know. 

Well, it turns out that the carriers do know.

Reddit user (and smartphone tetherer) kehrol received the email above from AT&T, which notes, "Our records show that you use this [tethering] capability, but are not subscribed to our tethering plan." The email also requests that he either stop tethering or pay for a more expensive tethering data plan. 

Users trying to figure out how AT&T knew about the tethering have concluded that it has something to do with TTL numbers of sent packets. However, it does not really matter how they know, the fact is they do. Now anyone who makes use of their unlimited data plan on other devices will have to be on the lookout for trouble from their carriers, especially if they use AT&T.

Whether you think it is ethical to tether your phone for free or not, it is still interesting to know that your carrier may be watching you closer than you think. 

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Aaron Orquia

Aaron Orquia is an associate editor at Pocketables. He has been using Android and Linux since he bought his first computer years ago, and his interest in technology, software, and tweaking both to work just right has only grown stronger since then. His current gadgets include a OnePlus One, a Pebble smartwatch, and an Acer C720 Chromebook.

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11 thoughts on “AT&T knew you were tethering all along, and now they're doing something about it

  • I just use mine for checking email, check a couple of websites when I can’t hit a wi-fi hotspot.
    You think they are looking at the “amount” of data being used, or do they have another way to tell if you are tethering?

  • Avatar of Steven L

    Good luck trying to catch me using Bluetooth to tether my iPad to my iPhone! One of those times I’m glad that my iPad looks like an iPhone to the sites I use, and the apps look like any other iOS app!

  • It is speculated that they check ttl numbers, if so it wouldn’t matter how much data you use, they will know youre using a second device. I’ll probably post about TTL numbers if it is fairly certain that ATT is using them, so watch for a post in the next couple days.

  • Avatar of MikeF74

    Can using a VPN get around this detection?

  • i wonder if ATT checks the outgoing USER AGENT STRING?

    after all, iphone and android browsers sends out a diff UAS than those on a desktop/laptop browsers.

    if that’s the case, you can easily change the desktop UAS to match that of the the smartphone…


  • Probably not, as I can change the user agent on my phone to look Like a desktop, so it wouldnt be reliable.

  • This is too easy to do, just checking amount of data transmitted/received will give you good indication if you are already using the tethering. They won’t care how much you tether as long as your usage is small.

    BTW, There are many ways to detect tethering, it is all very trivial to implement.

  • Avatar of tovarish

    Sounds like a very good idea unless they monitor the data usage and conclude you are tethering if you consume more data. Even then it is not easy to prove and might get ATT into trouble if they go this route.

  • you might have to eat your hat on that eventually, check your TTL, bluetooth tethering is just another network protocol and TTL hops work the same way. It decrements, they gotcha.

  • Yep, bluetooth won’t help you if they’re tracking ttl, so it doesn’t matter if your ipad looks like an iphone.

  • Hi! Good luck trying to catch me using Bluetooth to tether my iPad to my iPhone!


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