Hackers have released the first "jailbreak" for the iPhone 4 to enable users to run non-Apple approved third-party applications and sign up to a carrier of their choice.
The jailbreak comes less than a week after the US Copyright Office made it legal for users to jailbreak iPhones.
Jailbreaking any smartphone to make the operating system on that phone interoperable with an independently created application is "fair use", the US copyright authority said in its ruling.
Unlike previous methods for by-passing Apple's locking systems, the jailbreak for the latest iPhone is browser-based and does not require users to run the software on a computer.
The jailbreak has been released through the jailbreak.com website, and users simply have to visit the site using their iPhone browser to begin the jailbreaking process to modifies the iOS mobile operating system found on the iPhone, iPod touch and iPad.
But some users have reported that the latest jailbreak has disabled multimedia messaging and Facetime functionality, according to US reports.
The author of the jailbreak has indicated via Twitter using the handle "comex" that work has begun on a fix for these problems.