The main purpose of Jailbreaking for iPhone units is because there is a variety of a function that the iPhone operating system does not support. The operating system for iPhone is specifically designed to only run software that has an Apple-approved cryptographic signature and Jailbreaking or hacking is the only way to unlock this restriction. The concept of Jailbreaking is to replace the iPhone’s firmware. By replacing the firmware, this modifies the version that requires the signature. Jailbreaking is not 100 percent safe because Jailbroken iPhones is prone for different kinds of virus. Due to iPhone Jailbreaking, Apple released version 2.0 of iPhone’s Operating system which allowed third party applications under Apple’s SDK terms and conditions. Aside from Jailbreaking, iPhone units also experienced SIM unlocking. Upon purchase of iPhone unit, the SIM is locked only for AT&T. AT&T is the sole network carrier of iPhone in the United States. iPhone owners found a way to unlock the SIM for the reason that they cannot consider AT&T’s expensive monthly rates. Vendors of iPhone outside the United States like Hong Kong, Italy, New Zealand, and Russia began selling iPhone units unlocked to any carrier and without contract. In Australia, they still sell locked iPhone units, but can unlock it upon request. Things like find cell phone numbers on your iPhone have become more accessible with the ability to browse on its faster 3g network.