New Zealand's privacy commissioner is keeping a close watch on social networking site Facebook after it was discovered that it tracks websites that users visit, even when they are logged out.
Facebook also briefly allowed people to see who had removed them from their `friends' lists.
Australian blogger Nik Cubrilovic has shown that, when people log out of Facebook, rather than deleting its tracking cookies, the site modifies them, maintaining account information and other unique tokens that can be used to identify users.
Privacy Commissioner Marie Shroff said she had not yet confirmed the claims were correct. "But it's something we're looking at closely."
People often underestimated what the site did with their information, she said.
"If people are happy to share, fine – but they shouldn't be taken by surprise and they shouldn't underestimate just how valuable their information is to Facebook and other businesses.
"People need to start thinking about how far they're prepared for Facebook to go.
"It announced a number of new features last week including a way to make sharing of your information more automatic. Instead of you having to actively choose to share information, Facebook will do it for you (for example what music you're listening to).
"From a privacy perspective, we usually have greater concerns about `passive' sharing because it tends to catch a lot more people unawares."
Mr Cubrilovic said the only way to stop being tracked was to delete every Facebook cookie in the browser, or use a separate browser for Facebook.
His blog about the discovery was picked up by technology news sites around the world, but Facebook has yet to provide a response.
Mr Cubrilovic said he tried to contact Facebook to inform it of his discovery but did not get a reply.
He said there were significant privacy risks to users, particularly those using public terminals to access Facebook. "The question is what it will take for Facebook to address privacy issues and to give their users the tools required to manage their privacy and to implement clear policies – not pages and pages of confusing legal documentation, and `logout' not really meaning `logout'."
Meanwhile, although Facebook's new Timeline feature, which shows users a timeline of their activity on the site throughout the years, has not officially been switched on, many are using it already.
But inadvertently or by design, the Timeline feature also let people see which users had "unfriended" them.
It appears Facebook has now disabled this function.
- Fairfax NZ