Most browsers leave fingerprint that can ID users

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The vast majority of people surfing the web leave behind digital fingerprints that can be used to uniquely identify them, research released Monday by the Electronic Frontier Foundation suggests.

Using a website that compares visitors' browser configurations to a database of almost 1 million other users, EFF researchers found that 84 percent of visitors used setting combinations that were unique. When The Register visited the site using Firefox, it received a message that read: "Your browser fingerprint appears to be unique among the 837,411 tested so far." (Turning off javascript and Java with the NoScript plugin didn't change the results we got on one test PC, but on a second machine, use of NoScript significantly increased the number of browsers with the same fingerprint.)

EFF said that its logs are anonymized, but there's nothing stopping the organization - or indeed, any website in the world - from constructing a database of digital fingerprints belonging to each person who visits the site.

"In fact, several companies are already selling products that claim to use browser fingerprinting to help websites identify users and their online activities," EFF Senior Staff Technologist Peter Eckersley said in a release. "This experiment is an important reality check, showing just how powerful these tracking mechanisms are."

EFF's "panopticlick" website examines user agents, HTTP_ACCEPT Headers and dozens of other browser characteristics to calculate how many other visitors to the site displayed the same combination of settings. It then offers a variety of steps users can take to prevent their browser from displaying unique traits that can be tracked.

A PDF of the EFF's whitepaper is here. ®

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