How Unique Is Your Web Browser? (You're being tracked based on how unique your browser settings are)

How Unique Is Your Web Browser? (You're being tracked based on how unique your browser settings are):

"Abstract. We investigate the degree to which modern web browsers are subject to 'device fingerprinting' via the version and con figurtion information that they will transmit to websites upon request. We implemented one possible fingerprinting algorithm, and collected these fingerprints from a large sample of browsers that visited our test site, panopticlick.eff.org.

We observe that the distribution of our fingerprint contains at least 18.1 bits of entropy, meaning that if we pick a browser at random, at best we expect that only one in 286,777 other browsers will share its fingerprint. Among browsers that support Flash or Java, the situation is worse, with the average browser carrying at least 18.8 bits of identifying information. 94.2% of browsers with Flash or Java were unique in our sample.

By observing returning visitors, we estimate how rapidly browser fi ngerprints might change over time. In our sample, fingerprints changed quite rapidly, but even a simple heuristic was usually able to guess when a figerprint was an 'upgraded' version of a previously observed browser's fingerprint, with 99.1% of guesses correct and a false positive rate of only 0.86%.

We discuss what privacy threat browser fingerprinting poses in practice, and what countermeasures may be appropriate to prevent it."