Hacking iOS installed on an iPhone is easier done than said.
These are two different things:
- Jailbreak: Jailbreaking is done to install apps from non-Apple source (itunes App store) also called third-party apps.
- Unlock: Unlocking is done to remove any operator lock that has been installed. So an AT&T locked iPhone sold in USA can be operated anywhere in the world on any operator network.
Jailbreaking an iPhone does not unlock it. But before Unlocking an iPhone, it needs to be Jailbroken.
- Jailbreaking installs an App 'Cydia' on the iPhone. Cydia is used to add many features to iPhone.
- Use the search feature of this app to install 'Ultrasnow'. Installing Utrasnow Unlocks the iPhone
Following both steps above makes an iPhone usable on any operator around the world.
Step-by-step tutorials for all versions of iOS are available here.
Latest hacks for iPhone and other devices can be found on Dev-Team blog.