Apple is facing an investigation by the U.S. Congress after it emerged that a number of apps downloaded on to the iPhone will take a copy of the owner's address book — including phone numbers, addresses and other details — without fully alerting the user.

The public messaging service Twitter has also come under scrutiny after it emerged that its app for the iPhone and for Google's Android operating system takes a copy of the user's address book once it is given permission to “scan your contacts for people you know on Twitter” and then retains it for 18 months.

Two members of the U.S. Congress have written to Apple chief executive Tim Cook demanding answers to “claims that the practice of collecting consumers' address book contacts without their permission is common and accepted among [third-party] app developers.” Last week it emerged that Path, a social networking app, uploaded and kept a copy of new users' address books without consent. One developer, Dustin Curtis, wrote: “I did a quick survey of 15 developers of popular iOS apps, and 13 of them told me they have a contacts database with millions of records. One company's database has Mark Zuckerberg's cell phone number, Larry Ellison's home phone number and Bill Gates' cell phone number. This data is not meant to be public, and people have an expectation of privacy with respect to their contacts.” Congressmen Henry Waxman and GK Butterfield have demanded to know why Apple is not as protective of address data as it is of location data. The latter issue caused a storm in April 2011 when the Guardian revealed that the iPhone had an inbuilt database that effectively tracked the user's location. Apple updated the iPhone software soon afterwards to encrypt or remove that data.

The congressmen have given Apple until 29 February to respond.

Twitter, meanwhile, has acknowledged to the LA Times that the “Find friends” feature on its iPhone app downloads the user's entire address book to its servers, where the details are then kept for 18 months.

The only clue that the app gives to its aims are that it says it will “scan your contacts for people you already know on Twitter”.

Responding to the LA Times, a Twitter spokeswoman said that a forthcoming version of the app would use clearer language: “In place of ‘scan your contacts', we will use ‘Upload your contacts',” she told the paper.

The Android Twitter app does the same thing, the spokeswoman pointed out.

Apple or Twitter had not responded to requests for comment as this piece was being prepared for publication. — © Guardian Newspapers Limited, 2012

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