We don't track logged-out users, says Facebook

Facebook has attempted to shoot down claims that it leaves cookies on users' machines even after they log out of the social network. The response came after an Australian blogger alleged the site can still snoop on your web surfing after you've signed out.

Nik Cubrilovic, concerned about Facebook's approach to privacy, said that logging out doesn’t make a blind bit of difference, adding that Facebook still has ways to potentially track your behavior.

Cubrilovic’s conclusion after examining the behavior of Facebook’s cookies is simple: “Even if you are logged out, Facebook still knows and can track every page you visit.”

This is because instead of telling browsers to remove cookies when users log out, Facebook merely "alters" the state of those little parcels of data – including the cookie that stores your account number.

As a result, if you happen to pass by a page with a Facebook “like” button, "share" button, “or any other widget”, your information – including your account number – will be sent back to Facebook. And if you log into Facebook from a public terminal, those cookies could be left behind.

However, Facebook doesn’t agree. Whether or not Cubrilovic’s claim that he notified Facebook without response during 2010 is accurate, he certainly got a hair-trigger response from Facebook this time.

In a comment on Cubrilovic's blog, a Facebook engineer – identifying himself as staffer Gregg Stefancik – said that “our cookies aren’t used for tracking”, and that “most of the cookies you highlight have benign names and values”.

"Generally, unlike other major internet companies, we have no interest in tracking people," the insider added.