EFF: Forget cookies, your browser has fingerprints

IDG News Service - Even without cookies, popular browsers such as Internet Explorer and Firefox give Web sites enough information to get a unique picture of their visitors about 94 percent of the time, according to research compiled over the past few months by the Electronic Frontier Foundation.

The research puts a quantitative assessment on something that security gurus have known about for years, said Peter Eckersley, the EFF senior staff technologist who did the research. He found that configuration information -- data on the type of browser, operating system, plugins, and even fonts installed can be compiled by Web sites to create a unique portrait of most visitors.

This means that most Internet users are a lot less anonymous than they believe, Eckersley said. "Even if you turn off cookies and you use a proxy to hide your IP address, you could still be tracked," he said.

The data doesn't actually identify the Web user, but it creates a unique browser "fingerprint," that can be used to identify the user when he visits other Web sites.

Using JavaScript, Web sites are able to probe PCs and learn a lot. No single piece of data is enough to identify the visitor on its own, but when it's all strung together -- browser version, language, operating system, time zone details -- a clearer picture emerges. Some things -- what combination of plugins and fonts are installed, for example -- can be a dead giveaway.

And using the private mode offered by some browser-makers does nothing to stop this analysis. "They provide you with some protection against other people who may be in your house or who have access to your computer, but they haven't got to the point where they've provided protection against the companies that are profiling Web users," Eckersley said.

In fact, there are already a handful of companies have already started offering this kind of cookie-less Web tracking to help e-commerce sites identify fraudsters. Companies such as 41st Parameter, ThreatMetrix, and Iovation are widely used in the banking, e-commerce and social Web sites.

And the products work. Last August, when Serbian criminals started testing stolen credit cards by posting hundreds of US$1.99 transactions to the iReel.com online movie site each day, iReel turned to ThreatMetrix to get a fix on the fraudsters.

Using similar techniques to those described by the EFF, ThreatMetrix generated digital fingerprints of site visitors, which helped iReel know when a single user was trying to use hundreds of different credit cards, even when the fraudster was using proxy IP addresses, said Adam Altman, iReel's chief operations officer. "We were able to cut out a lot of the unnecessary transactions," he said.