The Web's New Gold Mine: Your Secrets

Hidden inside Ashley Hayes-Beaty's computer, a tiny file helps gather personal details about her, all to be put up for sale for a tenth of a penny.

The file consists of a single code— 4c812db292272995e5416a323e79bd37—that secretly identifies her as a 26-year-old female in Nashville, Tenn.

The code knows that her favorite movies include "The Princess Bride," "50 First Dates" and "10 Things I Hate About You." It knows she enjoys the "Sex and the City" series. It knows she browses entertainment news and likes to take quizzes.

"Well, I like to think I have some mystery left to me, but apparently not!" Ms. Hayes-Beaty said when told what that snippet of code reveals about her. "The profile is eerily correct."

Ms. Hayes-Beaty is being monitored by Lotame Solutions Inc., a New York company that uses sophisticated software called a "beacon" to capture what people are typing on a website—their comments on movies, say, or their interest in parenting and pregnancy. Lotame packages that data into profiles about individuals, without determining a person's name, and sells the profiles to companies seeking customers. Ms. Hayes-Beaty's tastes can be sold wholesale (a batch of movie lovers is $1 per thousand) or customized (26-year-old Southern fans of "50 First Dates").

"We can segment it all the way down to one person," says Eric Porres, Lotame's chief marketing officer.

One of the fastest-growing businesses on the Internet, a Wall Street Journal investigation has found, is the business of spying on Internet users.

The Journal conducted a comprehensive study that assesses and analyzes the broad array of cookies and other surveillance technology that companies are deploying on Internet users. It reveals that the tracking of consumers has grown both far more pervasive and far more intrusive than is realized by all but a handful of people in the vanguard of the industry.

• The study found that the nation's 50 top websites on average installed 64 pieces of tracking technology onto the computers of visitors, usually with no warning. A dozen sites each installed more than a hundred. The nonprofit Wikipedia installed none.

• Tracking technology is getting smarter and more intrusive. Monitoring used to be limited mainly to "cookie" files that record websites people visit. But the Journal found new tools that scan in real time what people are doing on a Web page, then instantly assess location, income, shopping interests and even medical conditions. Some tools surreptitiously re-spawn themselves even after users try to delete them.

• These profiles of individuals, constantly refreshed, are bought and sold on stock-market-like exchanges that have sprung up in the past 18 months.

The new technologies are transforming the Internet economy. Advertisers once primarily bought ads on specific Web pages—a car ad on a car site. Now, advertisers are paying a premium to follow people around the Internet, wherever they go, with highly specific marketing messages.

Read more in The Wall Street Journal...