Facebook criticised for 'tracking' logged-out users

The controversy was sparked by Nik Cubrilovic, an Australian technology entrepreneur, who found that even after he logged out of the social network, it delivered “cookies” to his web browser that could be used to track visits to other websites.

Cookies are small text files used by websites to store user preferences and the contents of online shopping carts, among other functions.

When users log out of websites cookies are often deleted, but Mr Cubrilovic found that Facebook only altered them, while continuing to store data such as his account ID.This unique identifier could be used to track logged-out users when they visit other websites that have integrated Facebook functions, such as the “Like” button, he said.

“Logging out of Facebook only de-authorizes your browser from the web application, a number of cookies (including your account number) are still sent along to all requests to facebook.com,” Mr Cubrilovic said in a widely-shared blog posting.

“The only solution is to delete every Facebook cookie in your browser, or to use a separate browser for Facebook interactions.

http://www.telegraph.co.uk/technology/facebook/8789942/Facebook-criticised-for-tracking-logged-out-users.html