OK, so you don’t go to any porn sites and may think this technology doesn’t affect you. Guess again and read on.
Kashmir Hill writes:
YouPorn is one of the most popular sites on the Web, with an Alexa ranking of 61. Those who visit the homemade-porn featuring site — essentially, a YouTube for porn enthusiasts — are subject to scrutiny, though, of the Web tracking variety. When a visitor surfs into the YouPorn homepage, a script running on the website checks to see what other porn sites that person has been to.
How does it work? It’s based on your browser changing the color of links you’ve already clicked on. A script on the site exploits a Web privacy leak to quickly check and see whether your browser reveals that the links to a host of other porn sites have been assigned the color “purple,” meaning you’ve clicked them before. YouPorn did not respond to an inquiry about why it collects this information, and tries to hide the practice by disguising the script with some easy-to-break cryptography.*
The porn site is not alone in its desire to know what other websites visitors have visited. A group of researchers from the University of California – San Diego trolled through the Web’s most popular sites to see which ones were collecting this information about visitors. They found it on 46 other news, finance, sports, and games sites, reporting their findings in a paper with the intimidating title, “An Empirical Study of Privacy-Violating Information Flows in JavaScript Web Applications.”
Read more on Forbes.
Hat-tip, @EFF.