23 May 2010

Removing "Flash Cookies" from your computer

Flash cookies (or "local shared objects") are explained in a Wired article:
More than half of the internet’s top websites use a little known capability of Adobe’s Flash plug-in to track users and store information about them, but only four of them mention the so-called Flash Cookies in their privacy policies, UC Berkeley researchers reported Monday.

Unlike traditional browser cookies, Flash cookies are relatively unknown to web users, and they are not controlled through the cookie privacy controls in a browser. That means even if a user thinks they have cleared their computer of tracking objects, they most likely have not...

Websites can store up to 100K of information in [flash cookies], 25 times what a browser cookie can hold. Sites like Pandora.com also use Flash’s storage capability to preload portions of songs or videos to ensure smooth playback.

All modern browsers now include fine-grained controls to let users decide what cookies to accept and which to get rid of, but Flash cookies are handled differently. These are fixed through a web page on Adobe’s site, where the controls are not easily understood...
More at the link.  After reading about flash cookies, I installed a Firefox add-on called BetterPrivacy.  It surveyed my hard disk and found 2000+ flash cookies that had been set by sites such as WaPo, The Onion, MSNBC, ESPN, the BBC, NASA, WhiteHouse.gov, Masters.com, and by lots of game sites.  I tediously reviewed them (because some flash cookies can be left in place to help certain sites function better when visited) and deleted 99% of them. 

What you do is up to you, but you should read about this and think about it.

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