Apple is giving a whole new meaning to locking your phone with its new screws.



In line with its infamous philosophy of maintaining absolute control over its products, sources said US Apple stores are replacing screws on iPhone 4s brought for servicing with tamper-proof screws to prevent anyone else from opening the device.



Kyle Wiens, chief executive of iFixit, a prominent Apple repair and parts supplier, said the purpose of the new screws is to keep people out of the iPhone and prevent them from replacing the battery. He said he noticed in November that screws were being switched.



"If you took your car in for service and they welded your hood shut, you wouldn't be very happy"," he said, comparing it to shutting owners out of their iPhones.



IFixit, based in San Luis Obispo, California, has become famous in the technology world for performing "teardowns" of Apple devices, often within hours or minutes of a new product launch. The company promotes repair to cut down on electronic waste that goes to landfills.



According to two people with first-hand knowledge of the practice, when a customer brings an iPhone 4 into a US Apple store for repair, tech staff swap out commonly-used Phillips screws, with which the device is shipped, and replace them with so-called "Pentalobe" screws.



Customers are not told about the switch, these people said.



It was not clear how widely used the replacement screws are, but one of these people said the screw swap was begun in the fall and is now standard practice at US Apple stores. This person said the iPhone 4 shipped with Pentalobe screws in Japan.



Apple had no comment for this story, but it is well-known that Apple discourages individual modifications of its products.



The iPhone 4 went on sale last year and became Apple's fastest-selling version of the iconic device. More than 16 million iPhones sold in the quarter ending December.



Apple will replace iPhone batteries free if the device is under warranty, but otherwise charges $US79.



Wiens said that with the old screws the iPhone 4 battery was easy to change although that was not known to many customers. "Apple wants to be in the business of selling you the new battery," Wiens said.



The world's largest technology company acts swiftly to protect its secrets. When an iPhone prototype was found by an outsider in a bar last year and sold to tech blog Gizmodo, Apple kicked up a furor and investigators raided a journalists' home.



Pentalobe screws require a screwdriver that is not commercially available, Wiens said. The screw is similar to a commonly used Torx screw, but has five points instead of six.



Wiens said iFixit, which sells repair kits for iPhones and other Apple products, searched everywhere for a Pentalobe screwdriver before specially commissioning a supplier to make one for them - and even that is not a perfect match, he said.



The Pentalobe screw first appeared on the battery section of a Macbook Pro laptop in 2009, Wiens said. It also can be found on the exterior of Apple's new MacBook Air notebook.

Reuters