bobbyblue's blog

Flash cookies are a new way of tracing your movement and storing a lot more information about you than with normal cookies. One major disadvantage of flash cookies is that you can’t locate them in your browser. They are not shown in the list of cookies that you can see when you take a look at the cookies that are currently saved in your web browser. Normal HTTP cookies can’t save more than 4 Kilobyte of data while Flash cookies can save up to 100 Kilobyte. If you want to try out how they work you could do the following.

Go to Youtube, increase or decrease the volume of the videos and delete all cookies afterwards. You will notice that the volume level is still at the same level when you close your browser and open it again. This is done with so called Local Shared Objects, better known as Flash cookies. The main question is of course how a computer can be checked for Flash cookies and how it would be possible to delete those cookies again.

Turns out that web site operators can use Flash applets embedded on their site to write information into a preference file stored on the computer that visits the site. One thing this preference file can be used for is recreating a browser cookie that may have been deleted, or to store other tracking information. The idea of using Flash as a means of hiding a tracking cookie on a machine bothers me because it is insidious. There are clear interfaces built into web browsers for managing regular cookies, and users can delete or reject them as they choose. Flash Cookies are hidden in user libraries and preference files, and to manage them you have to burrow into Adobe’s support site to find the applet that will manage the privacy settings for the Flash Player installed on your computer. Did you catch that? To manage the privacy settings of a program installed on your computer, you have to go to an external web site. That bothers me on a fundamental level. I should be able manage the software on my computer using tools on my computer, without having to go to a vendor’s web site.


Because Flash Cookies use preferences written elsewhere on the computer, they aren’t tied to a single browser. I visited the Adobe page containing my Flash privacy settings with 2 different browsers and saw the same list of sites that are storing information on my machine. So, in that way, Flash Cookies are even better than regular browser cookies for advertising use, because they can affect every browser you have installed. A Flash Cookie could identify you to an advertiser, even if you’ve never visited the site with this specific browser before!

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