Just hours ago, Apple released the fourth beta version of the upcoming iPhone OS 4 and it's already generating a lot of buzz.
Why so? Well, on top of some minor aesthetic changes, this fourth beta seems to be allowing AT&T customers to tether their iPhone's data connection. While many reports are suggesting this is a hint of sorts from AT&T about upcoming availability, we wouldn't count on it.
The cause for these reports stems from how tethering is handled by the iPhone. Indeed, the iPhone's tethering capability is regulated by carrier-specific settings stored in the carrier bundle, not by the OS itself. For example, if you pop a foreign sim card in your unlocked iPhone and connect it to iTunes, it will download the appropriate settings (if available) for this new carrier and push them to your iPhone. It will even inform you about it with the following prompt:
This carrier setting update is how your iPhone can tell if this specific carrier supports tethering and act accordingly. No need for a firmware update, just a click of a button.
So how come Beta 4 users are able to tether without AT&T updating its settings? Well, that's just glitch. It causes your iPhone to misinterpret its carrier-specific settings and leaves tethering activated. That's all there is to it, sorry. I mean you didn't really expect a feature announced all the way back in 3.0 to finally make it to the only US Carrier in time for the 4.0 launch did you?