"The issue affects tens of millions of Facebook application users, including people who set their profiles to Facebook's strictest privacy settings," Wall Street Journal has reported.
The publication noted the practice breaks Facebook's rules and renews questions about its ability to keep identifiable information about its users' activities secure.
Citing its own investigations, the daily said that many of the most popular applications or "apps" on Facebook have been transmitting and identifying information—in effect, providing access to people's names and, in some cases, their friends' names, to dozens of advertising and Internet tracking companies.
"Apps" are pieces of software that allows Facebook's 500 million users play games or share common interests with one another.
The report noted that all of the 10 most popular apps on Facebook were transmitting users' IDs to outside companies.
"The apps, ranked by research company Inside Network Inc (based on monthly users), include Zynga Game Network Inc's FarmVille, with 59 million users, and Texas HoldEm Poker and FrontierVille.
"Three of the top 10 apps, including FarmVille, also have been transmitting personal information about a user's friends to outside companies," the daily said.
Most of the applications on Facebook are made by independent software developers
Quoting a Facebook spokesperson, the report said the site was taking steps to "dramatically limit" the exposure of users' personal information.
"The apps reviewed by the Journal 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 daily noted.
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