Researchers at Princeton and Belgium's KU Leuven have uncovered a new web-tracking method that's nearly impossible to block. It's called "canvas fingerprinting," and can potentially follow users between sites even if they've disabled more conventional methods like cookies and aren't logged into Facebook. Instead, the tactic works by asking the browser to draw a hidden image, and using that image to track the unique properties of the browser. Researchers found the tactic being used on 5 percent of the top 1,000 sites on the internet, including Whitehouse.gov, YouPorn, The Blaze, and the official website for the State of California.

The source behind the fingerprinting may be AddThis, a suite of plug-in share tools that is found on many of the named sites. AddThis has been testing canvas fingerprinting on certain sites as part of the company's broader search for alternatives to cookie tracking. It's still unclear how effective the tactic, with one survey only showing a 90 percent success rate, and AddThis says the fingerprinting trials may soon end since the results are "not uniquely identifying enough." Still, as concerns over web privacy grow, it's a reminder that simply blocking cookies may not be enough.