The Electronic Frontier Foundation has created an on-line tool that details the wealth of information a Web browser reveals, which can pose privacy concerns when used to profile users.
The EFF's Panopticlick tool takes just a few seconds to pluck out information that a Web browser divulges when visiting a Web site, such as a user's operating system, version numbers for plug-ins, system fonts and even screen size, color and depth.

Taken together, that information is a unique fingerprint for a particular PC, which could be used to repeatedly identify a particular visitor a Web site, the EFF said.

The EFF, which has campaigned against intrusive on-line advertising systems, warns that advertising companies are already using digital fingerprinting techniques, wrote Peter Eckersley, an EFF staff technologist, on the organization's blog.

"They develop these methods in secret, and don't always tell the world what they've found," Eckersley wrote. "But this experiment will give us more insight into the privacy risk posed by browser fingerprinting and help web users to protect themselves."

Panopticlick anonymously records a visitor's system configuration and then compares it to a database of five million other configurations. On Friday, the Panopticlick Web site said it had collected 188,394 browser fingerprints so far.

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