Browser Fingerprinting

Although many users are aware of some tracking mechanisms, such as cookies, typically stored by the user’s browser for authentication or managing Web site preferences, they are less aware of other tracking mechanisms, how much information can be collected, and that a unique digital “fingerprint” of their browser can be identified by combining tracking techniques.

In addition to cookies, Web bugs are another common tracking mechanism—they are sometimes called Web beacons, tracking bugs, tracking pixels, 1×1 GIF, or clear GIF. These are undetectable objects embedded in a Web page. They can help track user activity such as which Web pages have been visited or if an e-mail has been read. Another method that can determine which Web pages a user visited relies on Web developers changing the color of a followed hyperlink. The use of Cascading Style Sheets (CSS) can make the hyperlink color easier to detect.

Local shared objects (LSOs), or Flash cookies, are collections of cookie-like data stored as a file on a user’s computer by applications such as Adobe’s Flash Player. Because LSOs contain data stored by individual Web sites or domains, they can be subverted for tracking purposes. LSOs are used to collect information on how people navigate the Web, even if the browser has been configured to delete cookies. LSOs have even been used to reconstruct cookies that the user deleted.