If you use a computer and you surf the Web, the Internet's open architecture has made you visible to the world. So claims The Hundredth Window, Charles Jennings and Lori Fena's exposé on Internet security--or the lack thereof. Regardless of how you feel about privacy, though, this book can help you understand the risks of Internet use--plus convince you to take some precautions to minimize them.

The proverbial hundredth window represents the most vulnerable link in a system. It derives from an allegory relating castle windows to potential security holes. If even one out of a hundred windows is left open, security becomes compromised. Since the Internet maximizes information sharing (admittedly a largely beneficial enterprise) would-be big-time marketers and shady characters can--without trying all that hard--spy on your Web clicking habits, read your e-mail, and even see files on your hard disk drive. This means you may receive spam from marketers who think they know what kind of stuff you like to buy--e-mail that can be helpful to some and aggravating to others. Sharing your name and other identifying personal information can cause you more serious problems: someone else could use that information to commit fraud or other crimes--and you would be responsible.

Now, it's unlikely you'd undergo the sort of nightmare invasion of your privacy that occurred in the movie Enemy of the State, but the exchange of personal information about Internet users is undeniably a multibillion-dollar business. It's the increasingly fervent desire of marketing executives to know intimate details about you so they can help you shop. Maybe this is no skin off your nose, but take this example: you have a parent or grandparent with a serious illness and so you spend time researching the illness on the Web; consequently, your name is marked as a potential high risk and passed on to insurers. Numerous variations on this scenario are possible, and this book can get you started on the road to protecting yourself from potential problems.

Experts on this topic, authors Jennings and Fena have compiled a series of easy steps to help you minimize your visibility in cyberspace. Their approach isn't terribly sophisticated--they suggest you clear out your Web-browser cookies and use fake information when registering on Web sites, for example--but it's effective. They also offer several handy techniques that erase your Web footprints, such as leaving your America Online member profile blank and using blocking software. The topic of Internet security can sometimes get relegated to the land of the paranoid. But in this case, the advice is sensible and the solutions are practical. --Teri Kieffer

Privacy, whether we like it or not, has gone public. We are only just beginning to recognize how the Internet has redefined the relationship between our private lives and the public sphere. Every time we personalize a Web site, join a mailing list, or purchase a book or CD online, we open our lives to an ever-widening data network that offers us scant protection from the prying eyes of corporations, governments, insurance companies, or criminals. Has the e-commerce revolution permanently eroded all personal boundaries, or is it still possible to protect one's personal information in an increasingly wired world?

Charles Jennings and Lori Fena have devoted their careers to this question, most notably as the founders of TRUSTe, the leading privacy assurance and monitoring organization on the Internet. They have been instrumental in developing standards for judging how Web sites use and protect the personal information they collect, and they have advised numerous corporations who recognize that trust is the key to economic growth and expansion in the e-commerce world.

Security experts often say that if you put bars across ninety-nine of your windows but leave the hundredth window open, the invaders can still get in. For computer privacy, then, the question becomes, How can you best monitor that hundredth window? Jennings and Fena answer that question by providing a comprehensive guide to privacy and security in today's fast-moving online world, identifying winning and losing strategies for users and businesses alike. They argue that with so much information about us accessible through the Internet, we now need to think of privacy less as an inalienable right and more as a personal skill to be practiced and sharpened regularly. And for companies doing business on the Web, they demonstrate the critical importance of ensuring a private and secure environment for one's customers.

The Hundredth Window is also an invaluable source of useful information for every citizen of the World Wide Web. Jennings and Fena offer their readers:

• An unsparingly honest assessment of how many popular Web sites handle privacy protection
• Guidelines for evaluating a site's trustworthiness
• Tips and tricks for protecting your private information while surfing online
• Strategies to avoid being followed on the Internet
• An advance look at likely new technologies that could put your privacy at risk

Far from predicting the death of privacy, Jennings and Fena provide the tools and the perspective that will enable us all to preserve our privacy as we enter the twenty-first century, enabling us to enjoy the many benefits that the Internet can offer.