updated 09:05 am EDT, Wed August 4, 2010
Requires using JailbreakMe first
The unofficial iPhone Dev Team has posted ultrasn0w 1.0-1, an update of its unlocking utility. The release is the first to unlock the iPhone 4, in addition to the iPhone 3G and 3GS. iPhone 4s must be on the 01.59 baseband, while the 3G and 3GS must be using 04.26.08, 05.11.07, 05.12.01 or 05.13.04.
The new ultrasn0w is being distributed through Cydia, an on-device platform for unofficial apps. To install Cydia, however, people must first jailbreak an iPhone 4 using JailbreakMe. As the website is believed to be based on a PDF exploit, Apple is likely to interrupt jailbreaking with a future iOS release, probably iOS 4.1.