Super Cookies Lurk in Your Browser

by | Aug 11, 2009 10:09 AM ET

Flash cookies aren't nearly this tasty. Nor would I recommend dunking them in milk.

Martin Harvey/Digital Vision/Getty Images

Don't get me wrong. I love most cookies, but browser cookies are not my favorite flavor. If you're unfamiliar, Web sites keep little text files on your computer that you download when you download the rest of the site. For the most part, cookies are used to the owners of the site track where else you go and what you do. It's not secretive, and not really all that nefarious -- they're doing it for marketing reasons.

Cookies can also be used for other purposes, though, and they're great for saving your personal preferences when you visit the same sites over and over. But if you decide that you don't want these cookies hiding out in your browser files, it's pretty easy to go into your browser preferences and flush them out. Or set your browser to remove them at the end of the day when you shut down your machine. You can also tell your computer not to allow them -- but it won't be long before you turn them back on, I bet. Functionality for many sites is so tied to cookies that it's sometimes hard to use a lot of them without cookies turned on.

OK, so that's the case for most cookies. But there's another set of cookies stored on your machine that can't be cleared out that way. Some people call them "super cookies," I'm guessing because they resist being deleted when you dump the others out. These are related to Flash-based Web sites. Wired's Ryan Singel wrote about it yesterday. These statistics come from a study by the University of California, Berkeley, and they're are a little alarming. Apparently half the sites on the Internet use Flash to track people, but very few actually tell you that's what's being done in their privacy policies.

Singel also said that some of these Flash cookies "re-spawn" regular cookies that you've deleted when you manually dumped them in your browser. The Web site has even started using Flash cookies, though the privacy policy for the site says only that users may be tracked. The government's looking into cookie policies, though, and the Berkeley report was submitted as part of that effort.

So what should you do if you don't want Flash cookies on your machine? If you use Firefox, the BetterPrivacy extension gets rid of them (I know this because Pandora doesn't remember me anymore and I have to log in each time I open my browser). Singel's article also mentioned CCleaner for PC and for Mac.

I'm sure that once this becomes public and people start cleaning these cookies from their machines that Web designers will find new ways to track you. How's that for some Tuesday optimism?

Also, before I go, I'd like to wish Apple co-founder, prankster and recent "Dancing with the Stars" contestant Steve Wozniak a happy 59th birthday!

If you'd like to read more on these and related topics, take a look at these links:

How Internet Cookies Work

Can the government see what Web sites I visit?

How Spyware Works

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