Users of unlocked iPhones have been warned that the next upgrade for the device will relock their phones and disable any third-party applications that have been installed.

Noted iPhone hacker "natetrue," creator of the iBrickr utility, posted a video clip on the Gizmodo blogthat showed one of the changes purportedly included in the iPhone 1.1.3 firmware upgrade: the ability to rearrange application icons on the iPhone's home screen.

Natetrue claimed that the update breaks unlocks - hacks made to allow the iPhone to work with non-authorised mobile networks - done with AnySIM, the popular for-free, open-source unlock utility. The upgrade also disables any installed third-party applications, and breaks the "jailbreak" applications used to install those unauthorised programs.

The 1.1.3 firmware update fixes the flaws that let hackers jailbreak "1.1.2, locking us out again, as expected," natetrue told Gizmodo.

Each time that Apple has updated the iPhone's internal software, third-party applications have been purged from the device, and the ability to unlock the phone has been lost. Apple last upgraded the iPhone in November to version 1.1.2, when it introduced the smart phone in the UK and Germany.

Another gadget blog, Gear Live, followed up an earlier screenshot gallery of 1.1.3 with a series of video clips to answer allegations it had spoofed the news. Among the new features of the upgrade, said Gear Live, are multi-recipient text messaging and location tracking in Google Maps. The latter, said Gear Live's Andru Edwards, is probably based on cell-phone tower triangulation, as opposed to GPS (global positioning system) technology.

Firmware 1.1.3 also lets users add HTML bookmarks to icons on the home screen, allowing easier access to web-based applications - the only Apple-authorised third-party efforts thus far. In February, 2008, however, Apple will introduce an iPhone software developer's kit (SDK), giving programmers a way to craft native applications for the iPhone.

Apple has not pre-announced the release of iPhone updates in the past, and is not expected to do so in the case of 1.1.3. Some pundits and bloggers, however, have speculated that it the upgrade might roll out as part of other iPhone news during MacWorld Conference & Expo, the trade show that starts on 14 January.