Facebook was hit by another privacy row after it emerged that millions of pieces of personal information from the site were being shared without users' consent.Vast quantities of data, including the names of individual members and their online 'friends', were passed to internet ad firms, with tens of millions of people thought to have been affected.
The leaks were possible even when members had deliberately set their privacy options to the maximum secrecy levels, reports the Daily Mail.
The practice violates Facebook's own rules on data protection and will raise questions about the company's ability to keep information about its members' activities secure, according to the Wall Street Journal.
Security experts warned that the details could be used - when combined with other publicly available information - to build up a detailed picture of an individual's interests, friendship circle and lifestyle.
Campaigners condemned what they called a "gross invasion of privacy" and warned users that Facebook was "not a private place".
Around 25 advertising and data firms were receiving the information. It was passed to them by firms whose 'apps' - games and other features - operate on Facebook and not by the social networking site itself.
Using the data allows advertisers to better target individuals with promotion for specific products.
The Wall Street Journal said the 10 most popular apps on the site were transmitting user IDs to outside companies, including the popular game FarmVille - which has 59 million users - Texas Hold, Em Poker and FrontierVille.
Monday night, Facebook said it had taken immediate action to disable all applications that violated the rules. But it is the latest privacy row to engulf the site, which has 26 million users in Britain alone.
