Evercookies
Evercookies, created by Samy Kamkar, are JavaScript-based applications which produce cookies in a web browser that actively "resist" deletion by redundantly copying themselves in different forms on the user's machine (e.g., Flash Local Shared Objects, various HTML5 storage mechanisms, window.name caching, etc.), and resurrecting copies that are missing or expired. Evercookie accomplishes this by storing the cookie data in several types of storage mechanisms that are available on the local browser. It has the ability to store cookies in over ten types of storage mechanisms so that once they are on your computer they will never be gone. Additionally, if evercookie has found the user has removed any of the types of cookies in question, it recreates them using each mechanism available. Evercookies are one type of zombie cookie. However, modern browsers and anti-malware software can now block or detect and remove such cookies.
Read more about this topic: Internet Privacy, Risks To Internet Privacy