According to a report in the Wall Street Journal, a large number of the most popular applications on Facebook — including all of the 10 most popular apps — have been improperly transmitting user info, including names and possibly names of friends to advertising and internet tracking companies.

Writes the Journal:

The issue affects tens of millions of Facebook app users, including people who set their profiles to Facebook’s strictest privacy settings. The practice breaks Facebook’s rules, and renews questions about its ability to keep identifiable information about its users’ activities secure.

The problem has ties to the growing field of companies that build detailed databases on people in order to track them online… It’s unclear how long the breach was in place. On Sunday, a Facebook spokesman said it is taking steps to “dramatically limit” the exposure of users’ personal information.

Among the apps mentioned in the Journal report are FarmVille, Phrases, Texas HoldEm Poker, FrontierVille, Causes, Cafe World, MafiaWars, Quiz Planet, Treasure Isle and Heart.

The Journal says the apps they investigated were sending Facebook ID numbers to at least 25 advertising and data firms, “several of which build profiles of Internet users by tracking their online activities.”

The report singles out one such firm, Rapleaf, which it says had added Facebook user IDs to the database of Internet users it sells to yet other firms. However, a VP for the company tells the paper, “We didn’t do it on purpose.”

Facebook in Privacy Breach [WSJ]

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