As I discussed here, the EFF is running an experimental site demonstrating that browsers ooze an unnecessary “browser fingerprint” allowing users to be identified across sites without their knowledge. One can easily imagine this scenario:
- Site “A” offers some service you are interested in and you release your name and address to it. At the same time, the site captures your browser fingerprint.
- Site “B” establishes a relationship with site “A” whereby when it sends “A” a browser fingerprint and “A” responds with the matching identifying information.
- You are therefore unknowingly identified at site “B”.
I can see browser fingerprints being used for a number of purposes. Some sites might use a fingerprint to keep track of you even after you have cleared your cookies – and rationalize this as providing added security. Others will inevitably employ it for commercial purposes – targeted identifying customer information is high value. And the technology can even be used for corporate espionage and cyber investigations.
It is important to point out that like any fingerprint, the identification is only probabilistic. EFF is studying what these probabilities are. In my original test, my browser was unique in 120,000 other browsers – a number I found very disturbing.
But friends soon wrote back to report that their browser was even “more unique” than mine! And going through my feeds today I saw a post at Tomek's DS World where he reported a staggering fingerprint uniqueness of 1 in 433,751:
It's not that I really think of myself as super competitive, but these results were so extreme I decided to take the test again. My new score is off the scale:
Tomek ends his post this way:
“So a browser can be used to identify a user in the Internet or to harvest some information without his consent. Will it really become a problem and will it be addressed in some way in browsers in the future? This question has to be answered by people responsible for browser development.”
I have to disagree. It is already a problem. A big problem. These outcomes weren't at all obvious in the early days of the browser. But today the writing is on the wall and needs to be addressed. It's a matter right at the core of delivering on a trustworthy computing infrastructure. We need to evolve the world's browsers to employ minimal disclosure, releasing only what is necessary, and never providing a fingerprint without the user's consent.