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Jailbreak Tether On Your iPhone? AT&T Wants To Have A Word With You

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Are you tethering your iPhone using a Jailbreak App? If so, AT&T wants to have a word with you – you’re costing them money and they know about it.

Yesterday and early this morning AT&T sent a text message to iPhone owners who use Jailbreak only Apps to enable tethering or consume massive amounts of data. Using tethering on your iPhone through a Jailbreak App not approved by AT&T is in direct violation of its TOS (Paragraph 1.3 of the Wireless Customer Agreement states) but the carrier has done nothing about it for the past couple of years – until now. AT&T is identifying heavy data users and those it suspects of using Jailbreak Apps then sending them a message that tethering + Data Pro plan will be added to their account.

For those crying foul and thinking of using this as an excuse to get out of their contract, it won’t work. The loophole to exit a contract and not be blasted with an early termination fee is your service rate arbitrarily increasing. An example of this is AT&T’s few cent text message rate hike – users had the same plan but were expect to pay a small amount more. Being switched to a Tethering + Data Pro plan would be a new plan change and not a rate change for an existing plan since you would no longer be on the ‘unlimited’ data plan.

How AT&T Knows About Jailbreakers

The most baffling (or troubling depending on who you talk to) aspect of AT&T’s mass message is how does the carrier know you’re using a Jailbreak-only method to tether? In short, they do and they don’t. AT&T can guess if you’re tethering without paying by checking the amount of data you consume. If data exceeds the normal levels of an iPhone during a certain amount of time, that would be an indicator someone is piping that data to their computer or they’re downloading a massive file. AT&T can also check the user agent of your browser and if it doesn’t match “Mozilla/5.0 (iPad; U; CPU OS 3_2 like Mac OS X; en) AppleWebKit/531.21.10 (KHTML, like Gecko) Version/4.0.4 Mobile/7B367 Safari/531.21.10, then it’s a tell-tall indicator another device is using the iPhone’s data connection. A typical user agent from your computer (in this case a beta of Firefox 3.0) would look like this: Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10.4; en-US; rv:1.9b5) Gecko/2008032619 Firefox/3.0b5 . As much as we’d like Firefox to be on the App Store, I’m sure AT&T’s IT department knows that’s not the case.

However, AT&T has more in depth tools to more accurately guess whether you’re jailbreak tethering or not. The smart minds at Reddit have compiled a list of potential methods AT&T would use to be almost certain of your tethering status. Reddit user byu146 gave his insight on how IP packets could quickly analyzed to determine its origin:

For all you wondering how they can tell:
All IP packets have something called a TTL associated with them. It stands for Time To Live. Every “hop” along the network from one router to the next reduces the TTL by one. When it reaches 0, the packet is dropped. This was introduced to keep routing problems from overloading the network. If for example, by some error a packet was going around in a circular path, the TTL would eventually reach 0 and prevent a packet storm.
The thing is, ALL routing devices do this. OSes use standard TTLs. For example, let’s say both your iPhone and laptop use 127 for the TTL. AT&T will receive packets from your iPhone with a TTL of 127, but since the packets from your laptop pass through your iPhone first, they arrive at AT&T with a TTL of 126. They can detect a tethered device this way.
EDIT: Some people below have suggested changing the default TTL of their tethered device (which is possible). I would just like to point out that the max TTL allowed is 255, and if the iPhone uses 255 as its default TTL, well there’s no way you can set it to 256.

AT&T Is Sending Warnings

Now that AT&T has a much better understanding of who’s tethering for free, the carrier is taking a much more proactive and aggressive approach to combat the problem. Yesterday night and this morning, AT&T sent a text message to subscribers it either knows or suspects of jailbreak tethering:

AT&T Free MSG: Did you know tethering your Smartphone to a computer requires a tethering plan? Pls [sic] call 888-860-6789 for details or visit

AT&T is also sending an email to select subscribers which as far as we know is different from those who received text messages:

Dear [Customer],

We’ve noticed your service plan may need updating.

Many AT&T customers use their smartphones as a broadband connection for other devices, like laptops, netbooks or other smartphones– a practice commonly known as tethering. tethering can be an efficient way for our customers to enjoy the benefits of AT&T’s mobile broadband network and use more than one device to stay in touch with important people and information. To take advantage of this feature, we require that in addition to a data plan, you also have a tethering plan.

Our records show that you use this capability, but are not subscribed to our tethering plan.

If you would like to continue tethering, please log into
your account online at Cell Phones and Cell Phone Plans – Wireless from AT&T, or call us
at 1-888-860-6789 Monday – Friday, 7 a.m. – 9 p.m. CST
or Saturday, 8 a.m. – 7 p.m. CST, by March 27, 2011
to sign up for DataPro 4GB for Smartphone Tethering.
Here are details on the plan:

DataPro 4GB for Smartphone Tethering
• $45 per month
(this gives you 4GB in total, combining both your smartphone data plan for $25 and the tethering feature, $20)
• $10 per each additional GB thereafter, added automatically as needed
• Mobile Hotspot capabilities are included for compatible Smartphones

If we don’t hear from you, we’ll plan to automatically enroll you into DataPro 4GB afterMarch 27, 2011. The new plan – whether you sign up on your own or we automatically enroll you – will replace your current smartphone data plan, including if you are on an unlimited data plan.

If you discontinue tethering, no changes to your current plan will be required.

It’s easy to track your usage throughout the month so there are no bill surprises. For example, we send you free text messages when you reach 65, 90, and 100 percent of your plan’s threshold. If you would like to monitor your account more closely, go to learn about other ways to track your data usage.

As a reminder, our smartphone data plans also include unlimited usage of Wi-Fi at no additional charge. AT&T smartphone customers can use Wi-Fi at home or on-the-go at any one of our more than 23,000 U.S. hotspots already included in your data plan.

Thank you for bringing your account up to date. We appreciate the opportunity to continue to serve your mobile broadband needs.



This is a very touchy subject as AT&T is not in the wrong to enforce its user policy but some subscribers feel justified as ‘Unlimited’ Data should be just that – Unlimited and not without restriction on where it is used. How do you feel about AT&T’s move against Jailbreak tethering? Did you receive a message from AT&T?

Kokou Adzo

Kokou Adzo

Kokou Adzo is a stalwart in the tech journalism community, has been chronicling the ever-evolving world of Apple products and innovations for over a decade. As a Senior Author at Apple Gazette, Kokou combines a deep passion for technology with an innate ability to translate complex tech jargon into relatable insights for everyday users.

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