Flash Cookies

Some people know what a cookie is, what it’s good for and how it can be abused. If you don’t here’s a very short summary:

  • Cookies are codes that web sites save to your computer
  • They’re used to help web sites remember who you are. E.g. when you log onto eBay and come back the next day, it remembers who you are.
  • Marketing companies use them to keep track of how many of their ads you saw and where you might have seen them

So they’re not really a bad thing but marketing companies use them to track things about you. Then there are programs that try to delete them off your PC. Usually these programs are branded with words like “anti-spyware”, this isn’t completely accurate but that’s where you’ll see them. This is all fine so far.

And you can always delete cookies yourself. In Internet Explorer there’s an option in the Tools menu. All other browsers have similar options, usually in a tools or settings menu.

But there’s another kind of cookie that often gets overlooked – they’re called Flash cookies.

Unlike regular cookies, Flash cookies are not stored in your web browser’s settings. Deleting all privacy data leaves Flash cookies alone. Even deleting all cookie files off your drive skips Flash cookies.

Flash has a feature that lets web sites store a bit of information on your computer, just like a regular “cookie”. By itself this is harmless, but some developers have taken advantage of its features and use them to track you just like regular cookies. This by itself could be seen as a minor annoyance, it’s not dangerous.

But it’s also possible for a web site to restore a cookie that you deleted. Now this is a misuse of privacy. You see, when you tell your computer to delete all privacy data, and it later reappears, things are happening against your will – this is morally bad. The way they do it is developers create some code that uses Flash to store a copy of a cookie and if the cookie is gone it rewrites it.

What can you do about it?

On Windows you can install “Better Privacy” or “Ccleaner”.

On Mac OS X you can install “Flush.app” or delete the Flash cookie files the hard way.

There’s also a great deal more information in this article.

It’s now up to Adobe (the company that makes Flash) and web browsers to treat this as a privacy bug and to improve their browsers.

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