Major technology brands behind over 30 of the top Apple iPhone applications, including Twitter, Facebook and Foursquare, have received letters from US lawmakers requesting information on how the apps collect consumer data.
The letters were sent out on Thursday to companies with products in the App Store's "iPhone Essential" area, as a part of an ongoing inquiry by the US House Energy and Commerce Committee, and they were given until 12 April to respond to the request.
The letter listed the recent revelation that social networking tool Path was accessing and uploading address book data from users' devices without permission as a key motivation for the inquiry.
"Last month, a developer of applications ('apps') for Apple's mobile devices discovered that the social networking app Path was accessing and collecting the contents of his iPhone address book without having asked for his consent," read the committee's letter to Facebook.
"Concerns were subsequently raised about the manner in which apps can access photographs on Apple's mobile devices. We are writing to you because we want to better understand the information collection and use policies and practices of apps for Apple's mobile devices with a social element."
V3 contacted Facebook, Twitter and Foursquare for comment on the letter, with Foursquare saying "we don't have anything to share yet" and Twitter refusing to comment. Facebook had yet to reply.
Though the letter was sent to firms using Apple's platform, the news comes in the midst of wider concern over mobile permissions, with apps on Google's Android operating system also falling under suspicion.
Since the discovery lawsuits have been mounted by consumers against both the app's developers and Google and Apple.
Earlier in March a lawsuit was mounted at the US District Court for the Western District of Texas accusing 18 companies, including Facebook, Apple, Twitter and Yelp, of distributing privacy-invading mobile apps.
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