AAAI Publications, 2010 AAAI Spring Symposium Series

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Flash Cookies and Privacy
Ashkan Soltani, Shannon Canty, Quentin Mayo, Lauren Thomas, Chris Jay Hoofnagle

Last modified: 2010-03-23


This is a pilot study of the use of “Flash cookies” by popular websites. We find that more than 50% of the sites in our sample are using Flash cookies to store information about the user. Some are using it to “respawn” or re-instantiate HTTP cookies deleted by the user. Flash cookies often share the same values as HTTP cookies, and are even used on government websites to assign unique values to users. Privacy policies rarely disclose the presence of Flash cookies, and user controls for effectuating privacy preferences are lacking.


privacy; tracking; flash; cookies; local stored objects; usability; online advertising; behavioral targeting

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