Do you know who's tracking you when you're surfing the Web -- and what they do with the information? A new study suggests you may not know as much as you think.

The study by researchers at the University of California-Berkeley (PDF), which was released late Monday, indicates that Web users may be tracked ("bugged," as the researchers put it) by dozens of sources on a visit to a single site. In a single month, they found 100 monitoring agents on one site, blogspot.com.

While many of the trackers used on blogging sites are low-level monitors used by bloggers to see who's reading their content, the big companies -- such as Google -- are also tracking a large portion of Web traffic, the report says. "We found five trackers overall operated by Google, including Analytics, DoubleClick, AdSense, FriendConnect, and Widgets," the researchers say.

"Among the top 100 Websites this project focused on, Google Analytics appeared on 81 of them," the report states. "When combined with the other trackers it operates, Google can track 47 of the top 50 Websites, and 92 of the top 100 Websites. Further, a Google-operated tracker appeared on 348,059 of 393,829 distinct domains tracked by Ghostery in March 2009 -- over 88 percent of the domains tracked by Ghostery that month."

Even if users know their Web activity is being tracked, they have no way of knowing how that data is being used, the researchers observe. "In our analysis of privacy policies, 36 of the Websites affirmatively acknowledged the presence of third-party tracking," the study states. "However, each of these policies also stated that the data collection practices of these third parties were outside the coverage of the privacy policy. This appears to be a critical loophole in privacy protection.

"In our analysis of the privacy policies, we found that 46 of the top 50 companies affirmatively state that they share data with affiliates, and the four remaining were unclear," the researchers report. "We sent each company a request via email or an online Web form for a list of each affiliate they may share data with. We received 14 replies, but none included the lists we asked for. Most stated that they do not disclose corporate information. Based on our experience, it appears that users have no practical way of knowing with whom their data will be shared."

While sharing data with "affiliates" may not sound particularly compromising, the researchers point out that many large companies have hundreds of affiliates, sometimes in completely different lines of business. "MySpace, one of the most popular social networking sites (especially among younger users), is owned by NewsCorp, which has over 1,500 subsidiaries," the study states. "Bank of America has over 2,300. It should be noted that these numbers include several foreign affiliates."

Some companies that do Web tracking maintain users don't care that they're being tracked, noting the relatively low number of privacy complaints filed with organizations like the Federal Trade Commission and TRUSTe each year. But the researchers dispute this conclusion.

"That would be a misinterpretation of the data," the study says. "It is apparent from our research that users do care. The low number of complaints simply conforms to our hypothesis that users file complaints only when two conditions are met: 1) they perceive an invasion of their privacy, and 2) they know where to file a complaint." Most users don't recognize how data from passive monitoring tools might affect their privacy, and even if they did, they wouldn't know where to file a complaint, the researchers say.

Current regulations that allow third-party Web tracking without the user's permission do little to protect the user's privacy, the study states. "Third-party trackers are not governed by a Website's privacy policy. Therefore, they have no incentive to allow users to view or delete information collected about them. In addition to this lack of participation, users have no ability to avoid third-party tracking. There is no opt-out, let alone opt-in."

The researchers recommend that new regulations be passed to allow users to find out more about how their browsing data is tracked and used, and that they be able to control the collection and use of that data.

"We recommend regulation by which both Websites and third-party trackers must allow users to see all the data that has been collected about them, not just user-provided information," the researchers state. "Additionally, users should also be allowed to see with whom their data has been shared. The imposition posed upon companies by such a requirement could be greatly mitigated by merely requiring that Websites provide users with the information they have about the user in a form no less convenient than the form in which it is available to the company."

The researchers further recommend that "companies request permission from users before sharing data about them with any outside party, regardless of affiliation. The presence and purpose of third-party tracking should also be made more salient in the minds of users. We recommend that all browser developers provide a Ghostery-like function in their browsers that alerts users to the presence of third-party trackers."

Much of the enforcement of these new regulations would fall to the FTC, the researchers recommend. The FTC would have to provide a better means for users to find out how their browsing data is being tracked and used, and a better process for filing complaints against companies that misuse the data, the study says.

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