Recently, online properties like Hulu, MSN and Flixster have been caught using a tougher version of the common cookie. These "supercookies" (aka "Flash cookies" and "zombie cookies") serve the same purpose as regular cookies by tracking user preferences and browsing histories. Unlike their popular cousins, however, this breed is difficult to detect and subsequently remove. These cookies secretly collect user data beyond the limitations of common industry practice, and thus raise serious privacy concerns.