How does evercookie work? It stores cookie data in several different manners in your browser, including HTTP, Flash, force-cached PNG images, various HTML5 storage systems, web history, and SQLite. If evercookie detects that you've been deleting your cookies, the program recreates your cookies.
Created by Samy Kamkar (who spawned a MySpace worm in 2005), evercookie was built in one day to make people more aware of the privacy issues inherent in tracking cookies, whether traditional HTML or Flash, according to threatpost.com. Want to experiment with evercookie on your own? The code is open source, and available at Kamkar's Website so that you can install it on your own webserver.
At present, one of the ways around evercookie's persistence is Safari's Private Browsing feature, which blocks all of evercookie's methods. Other browsers might stand up to evercookie's means of keeping cookies around, though Kamkar has not performed exhaustive testing. What's a user to do? Be careful about which browsers you accept cookies from, and keep tabs on HTML5 as it is developed. Some criticize the HTML5 standard for emphasizing functionality rather than security, something that evercookie exploits.
More security nerdery from PCWorld's GeekTech blog: