It depends largely on what version of the software you are running. There is a lag time of a few weeks between new iPhone software releases and public hacks to jailbreak them. Small changes are generally introduced in new versions to make breaking into it a little bit harder each time. The good news is that once a new jailbreak has been written, all of the free tools available are updated to make it possible for just about anyone to go through the process.
There are many free tools available to jailbreak the iPhone, some more reliable than others. The best tools are full-service utilities that also allow you to set up a shell and install third party software with little effort. The best of breed tools include:
- iNdependence (http://code.google.com/p/independence/“) : iNdependence is a utility for Mac OS X that performs jailbreak, activation, SSH installation, and even installation of ringtones, wallpaper, and third-party applications on the iPhone. iNdependence is under the GPL, and the author has made a library available called libPhoneInteraction, allowing developers to write other tools to communicate with the iPhone.
- AppSnapp (http://www.jailbreakme.com) : Users running version 1.1.1 of the iPhone firmware can navigate to this web site using their iPhone and have the entire jailbreak process performed remotely. AppSnapp takes advantage of a vulnerability in one of the iPhone’s image libraries to break into the phone. What’s cool about this site is that it not only jailbreaks your phone, but it also fixes the vulnerability so that nobody else can maliciously take advantage of the phone. Version 1.1.1 and later of AppSnapp also patch the iPhone software to allow third-party applications, and installs AppTapp, the NullRiver installer, which can then be used to stage your iPhone for development.
- AppTapp (http://iphone.nullriver.com) : Nullriver is a software manufacturer out of Ontario, Canada, and the designer of a package installerfor the iPhone. Installer allows you to install any application on your iPhone that is included in their repository using a few easy taps. The installer software itself works with most versions of the iPhone software, but the installer’s installer (if that makes sense) is capable only of jailbreaking iPhone firmware v1.0.x. The previous tool in this list, AppSnapp, automatically installs AppTapp on v1.1.1 devices. AppTapp is also useful for the software downgrade procedure, explained next.
- ZiPhone (http://www.ziphone.org) : ZiPhone is a jailbreak technique developed by the iPhone Dev Team. It was kept under a heavy shroud of secrecy in anticipation of the Apple SDK, but it was eventually leaked by one of the dev team’s former members. ZiPhone has since been developed beyond a simple jailbreak technique and many other utilities have been added to it, including a full unlock for all iPhones up to OTB (Out-ofthe-Box) v1.1.3.