Major websites such as MSN.com and Hulu.com have been tracking people's online activities using powerful new methods that are almost impossible for computer users to detect, new research shows.
The new techniques, which are legal, reach beyond the traditional "cookie," a small file that websites routinely install on users' computers to help track their activities online. Hulu and MSN were installing files known as "supercookies," which are capable of re-creating users' profiles after people deleted regular cookies, according to researchers at Stanford University and University of California at Berkeley.
Websites and advertisers have faced strong criticism for collecting and selling personal data about computer users without their knowledge, and a half-dozen privacy bills have been introduced on Capitol Hill this year.
The spread of advanced tracking techniques shows how quickly data-tracking companies are adapting their techniques. When The Wall Street Journal examined tracking tools on major websites last year, most of these more aggressive techniques were not in wide use. But as consumers become savvier about protecting their privacy online, the new techniques appear to be gaining ground.
Stanford researcher Jonathan Mayer, a Stanford Ph.D. candidate, identified what is known as a "history stealing" tracking service on Flixster.com, a social-networking service for movie fans recently acquired by Time Warner Inc., and on Charter Communications Inc.'s Charter.net.
Such tracking peers into people's Web-browsing histories to see if they previously had visited any of more than 1,500 websites, including ones dealing with fertility problems, menopause and credit repair, the researchers said. History stealing has been identified on other sites in recent years, but rarely at that scale.
Gathering information about Web-browsing history can offer valuable clues about people's interests, concerns or household finances. Someone researching a disease online, for example, might be thought to have the illness, or at least to be worried about it.
Supercookies are stored in different places than regular cookies, such as within the Web browser's "cache" of previously visited websites, which is where the Microsoft ones were located. Privacy-conscious users who know how to find and delete regular cookies might have trouble locating supercookies.
The new techniques, which are legal, reach beyond the traditional "cookie," a small file that websites routinely install on users' computers to help track their activities online. Hulu and MSN were installing files known as "supercookies," which are capable of re-creating users' profiles after people deleted regular cookies, according to researchers at Stanford University and University of California at Berkeley.
Websites and advertisers have faced strong criticism for collecting and selling personal data about computer users without their knowledge, and a half-dozen privacy bills have been introduced on Capitol Hill this year.
The spread of advanced tracking techniques shows how quickly data-tracking companies are adapting their techniques. When The Wall Street Journal examined tracking tools on major websites last year, most of these more aggressive techniques were not in wide use. But as consumers become savvier about protecting their privacy online, the new techniques appear to be gaining ground.
Stanford researcher Jonathan Mayer, a Stanford Ph.D. candidate, identified what is known as a "history stealing" tracking service on Flixster.com, a social-networking service for movie fans recently acquired by Time Warner Inc., and on Charter Communications Inc.'s Charter.net.
Such tracking peers into people's Web-browsing histories to see if they previously had visited any of more than 1,500 websites, including ones dealing with fertility problems, menopause and credit repair, the researchers said. History stealing has been identified on other sites in recent years, but rarely at that scale.
Gathering information about Web-browsing history can offer valuable clues about people's interests, concerns or household finances. Someone researching a disease online, for example, might be thought to have the illness, or at least to be worried about it.
Supercookies are stored in different places than regular cookies, such as within the Web browser's "cache" of previously visited websites, which is where the Microsoft ones were located. Privacy-conscious users who know how to find and delete regular cookies might have trouble locating supercookies.
