The Electronic Frontier Foundation
have a neat tool out: the
Panopticlick. Many folks don’t know this, but every time you
visit a web page your web browser sends lots of information to the web
server you’re talking to—stuff like what web browser
you’re using, what sort of pages you can read, which plugins you
have installed and so forth. This is necessary in order for the remote
web server to answer you appropriately. But it can be used to identify
you.
How? Imagine that your web browser is just describing you: it might
say that you have brown hair, blue eyes, fair skin, a mole on your
left cheek, a slight limp, prefer wearing plaid shirts, never wear a
hat, have a birthmark on your left ankle and so forth. None of those
data are unique: the world is full of brunettes, full of folks with
blue eyes and so forth. But there’re not that many
brown-haired, blue-eyed, left-cheek-moled folks out there—and
still fewer have fair skin, and fewer still have a slight limp, and
fewer still have birthmarks on their left ankles.
Why does this matter? Well, it matters in the same sense that
fingerprints matter. Every time you touch something, you’re
leaving fingerprints—and every time you visit a website
you’re leaving a fingerprint. Pretty nifty, huh?