Whenever you surf the Web, you leave yourself open to being snooped upon by web sites. They can track your online travels, know what operating system and browser you're running, find out your machine name, peer into your clipboard, uncover the last sites you've visited, examine your history list, delve into your cache, examine your IP address and use that to learn basic information about you such as your geographic location, and more. To a great extent, your Internet life is an open book when you visit. Don't believe me? Head to http://www.anonymizer.com/privacytest/. This page, run by the Anonymizer.com web service, tells you your IP address and machine name. And that's just a start. Click the links such as Exposed Clipboard and Geographical Location. You'll see just a small sampling of what web sites can learn about you. Figure 1 shows a web site reporting on my IP address, the contents of my clipboard, my browser information, and my geographic location. It's close enough; I live in Cambridge rather than Boston, and we generally require that people turn over their passports at the border.

Figure 1. The Anonymizer.com web service, exposing my current geographic locationMuch of the reason why web sites can find out this information about you is due to the trusting nature of the Internet's infrastructure and is inherent in the open client/server relationship between your web browser and the servers on the sites you visit. But a lot of it also has to do with the ability to match up information from your PC to information in publicly available databases—for example, databases that have information about IP addresses.The best way to make sure web sites can't gather personal information about you and your computer is to surf anonymously; use an anonymous proxy server to sit between you and the web sites you visit. When you use an anonymous proxy server, your browser doesn't contact a web site directly. Instead, it tells a proxy server which web site you want to visit. The proxy server then contacts the web site, and when you get the web site's page you don't get it directly from the site. Instead, it's delivered to you by the proxy server. In that way, your browser never directly contacts the web server whose site you want to view. The web site sees the IP address of the proxy server, not your PC's IP address. It can't read your cookies, see your history list, or examine your clipboard and cache because your PC is never in direct contact with it. You're able to surf anonymously, without a trace.There are two primary ways to use anonymous proxy servers. You can run client software on your PC, which does the work of contacting the server for you, or you can visit a web site, which does the work of contacting the server.