SOME OF THE MOST POPULAR Facebook apps have been sending user’s names and their friends’ names to third parties, such as internet tracking companies and advertisers.

An investigation by the Wall St Journal claims that the practice, which is in breach of Facebook’s rules, will even provide the user ID of people who have opted for the highest privacy settings.

The newspaper reports that all of the 10 most popular apps for the social networking site were sending user’s ID number, which is unique to each member, to external companies.

Some of those third party companies compile Internet user databases and at least one, RapLeaf Inc, sells its databases.

The apps named include Farmville, Texas HoldEm Poker, Mafia Wars and IHeart. Farmville alone had over 80m users last February.

Anyone can use a Facebook ID number to look up a person’s name, even if they have the top privacy settings on their profile.

A spokesperson for Facebook said the company was working to limit the transfer of user information, but said that having an ID number doesn’t permit someone accees to anyone’s private information on Facebook.

RapLeaf Inc said it hadn’t intended to pass on Facebook user IDs, while Zynga Games (which created Farmville) said it has a “strict policy of not passing personally identifiable information to any third parties”.

Gawker recommends turning off apps entirely in order to prevent them from sending any account information. This can be done by going to your account privacy settings and editing the settings for “Applications and Websites”.