EFF staff technologist Peter Eckersley noted in the blog post that there appears to be no easy way for users of such sites to avoid being tracked in this fashion.

To mitigate the risk, users of social networking sites need to disable flash cookies and ensure that all other cookies are deleted when the browser is closed, Eckersley wrote.

Certain Firefox extensions are also available that allow users to control when third-party sites can include content or run code on their browsers and plug-ins are available to help them opt out of targeted advertising cookies, he wrote.

But the steps can be hard to follow and can limit browser functionality. "We're fearful that the vast majority of Internet users will continue to be tracked by dozens of companies -- companies they've never heard of, companies they have no relationship with, companies they would never choose to trust with their most private thoughts and reading habits," he wrote.