Facebook keeps a virtual eye on its users even when they have logged out of the social network, an Australian technologist reveals.

Fairfax Media reports that Wollongong-based Nik Cubrilovic conducted tests revealing that when a user logs out of Facebook, the site maintains account information and other Web tokens that can be used to identify him to the point that the network is able to track the user where he goes next on the Web.

Cubrilovic said Facebook should delete its tracking cookies instead of merely modifying them once the user has logged out. If Facebook is not doing this, the user who wants to protect his privacy must be proactive.

"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,'" Cubrilovic told Fairfax.

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

Cubrilovic was previously involved with technology blog TechCrunch and online storage company Omnidrive. He is currently working on an unnamed start-up firm.

Stephen Collins, spokesman for the users' lobby Electronic Frontiers Australia, said he hopes Cubrilovic's pronouncements would encourage users to learn more about the privacy issues at Facebook.

''Facebook, once again, are doing things that are beyond most users' capacity to understand while reducing their privacy. That's just not cool. I'd go so far as to say it's specifically unethical,'' he told Fairfax.

Cubrilovic said he tried to contact Facebook to let it know of his findings, but did not get a reply. He said there were significant risks to the privacy of users, particularly those using public terminals to access Facebook.

"Facebook are front and centre in the new privacy debate, just as Microsoft were with security issues a decade ago," Cubrilovic said.

Fairfax said it had tried to get Facebook's side on the matter but the social network has not yet responded.