A new hack should allow T-Mobile subscribers to use iOS' personal hotspot feature for free without jailbreaking, says the workaround's creator, iTweakiOS. A component buried in iOS, CommCenter, normally checks the signatures in carrier PLIST files and prevents those files from being usably edited. The T-Mobile hack
is said to bypass CommCenter checks while also being relatively easy to apply.
iTweakiOS notes that the scheme should in theory work for other GSM carriers, but that applying it to AT&T demands that people "tinker around and test a bit to get it operational." This includes some PLIST editing.
Carriers will often charge extra for the ability to use iOS' hotspot feature, which like its equivalents on other platforms lets people tether devices via Wi-Fi. In some cases tethering can be turned on without paying for it or hacking, but at the risk of having data access temporarily throttled or shut off. Attention is usually only aroused by high-intensity traffic, such as torrents and/or large file downloads.