Facebook has caused controversy by allowing developers of apps access to some of its 500 million users’ most sensitive information, including telephone numbers and addresses.

The social networking site founded by Mark Zuckerberg, whose own stake is worth $12bn (£7.5bn), advised its app-developers about how to obtain Facebook users’ personal details.

The post, intended for Facebook’s app-designers, was leaked and while Facebook users must give app-developers permission to access their details, it is very likely that many people who have clicked their approval plenty of times before will not notice the change in terms and will pass on

contact details unknowingly, leaving them more vulnerable to becoming victims of spam.

internet security analysts and privacy experts are advising Facebook users to remove their phone numbers and addresses from their profiles immediately.

Rogue Facebook app-makers have been known to scam people by using their phone numbers to steal money.

Facebook, which gives advertisers the ability to target users according to their stated interests, geographical location and other insights, has come under increasing criticism for the way it handles its users’ private information.

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Speaking about this latest backlash, Graham Cluley, senior technology consultant at IT security and control firm Sophos, said: “You can imagine, for instance, bad guys could set up a rogue app that collects mobile phone numbers and then uses that information for the purposes of SMS

spamming or sells the data to cold-calling companies.

“The ability to access users’ home addresses will also open up more opportunities for identity theft, combined with the other data that can already be extracted from Facebook users’ profiles.

“You have to ask yourself – is Facebook putting the safety of its 500-plus million users as a top priority with this move?”

Facebook said the move would lead to more efficient apps for its users.

The official Facebook blog post on the subject explains that the company says: “Because this is sensitive information, we have created the new user address and user mobile phone permissions. These permissions must be explicitly granted to your application by the user via our standard

permissions dialogs.”

It also says that Facebook users are merely able to grant external developers the ability to see their own details, rather than those of their friends.

But it is often unclear who exactly is behind the small and seemingly harmless pieces of software available via Facebook, which many users enjoy signing up for in order to brighten up their profile pages or to play games or quizzes with friends. Facebook has opted against a systematic

program of vetting potential applications, such as that by Apple.