It seems like every other day I hear about a new threat to online privacy or about another Web site misrepresenting its privacy claims. The latest news--that the ubiquitous ad service DoubleClick tracks online users through the use of invisible "Web bugs"--bugged me to the point where I started thinking: How can we stop the DoubleClicks of the world tracking our every move on the Web?

Maintaining privacy when surfing the Web is no easy task, and it has become a big concern for more than just privacy advocates. All Internet users risk becoming part of massive databases that profile their actions every time they surf the Web. While Congress interminably mulls over legislation to protect users, companies have free rein to track all their visitors' activities and link information they collect from order forms or surveys to their users' clickstreams--the path of links a Web surfer follows in each foray across the Net.

To answer my own question, I tested three online privacy services that promise to throw trackers off your scent as you surf. Anonymizer's Anonymizer Surfing, Privada's PrivadaControl, and Zero-Knowledge's Freedom all offer a similar service: complete and utter freedom from the tracking effects of cookies, Web bugs, and other monitoring activities.

By no means are these the only products that can perform such tasks, but these are the most well established and best-known products available. I'll tell you what makes each of these three services unique and which one might be right for you.

The Anonymizer

Anonymizer.com

Recommended for: No-frills Internet users who want only to mask their identity to Web sites.

Price: Free for basic surfing; $15 for three months or $50 per year for premium features such as ad filtering and encrypted cookies.

Download: No download or software installation required for this Web-based service.

Anonymizer's Web proxy service, the oldest service of its type on the Web, loads sites' pages through its server, which intervenes and obscures your IP address (the unique address that identifies your PC on the Internet) from prying Web sites. Using the free component of this service is extremely simple: Just type the URL of the site you want to view into the box labeled "Free Anonymous Surfing" on its front page. Thereafter, every link you click in the same browser window will filter through Anonymizer's service--which slows down the loading process a bit.

The paid version, called Anonymizer Premium Surfing, offers some additional features: You can set the service to store encrypted cookies for sites you visit frequently, thus avoiding having to reenter passwords. The service also offers filtering of Web page advertisements, something that substantially speeds up page loading from many sites.

PrivadaControl

Privada

Recommended for: Price-sensitive Web surfers who want to block cookies and potentially troublesome programs, such as ActiveX controls or Java applets.

Price: $5 per month of use.

Download: 8.9MB application; download required.

Privada's PrivadaControl functions like Anonymizer's online service, with a twist: Instead of entering the addresses of Web pages into a Web-based form, users of PrivadaControl simply surf as they normally would. The Java-based PrivadaControl application that you install on your hard drive directs the Internet traffic through Privada's secure network, where, as with Anonymizer, Privada's servers then pull down the Web sites you want to see.

The small PrivadaControl Control Center applet that lives on the desktop when you install the application allows you to quickly block cookies or other active content, such as ActiveX controls or Java applets, that could potentially compromise your privacy, reporting your online behavior in the background without your even knowing. The one problem I discovered with Privada is that, once I installed the paid version, Web page loading still takes substantially longer than it would on an unprotected computer.