Each of the following techniques for protecting personal information can help reduce the risk of at least some of the bytes flowing over the Internet. They aren't perfect. Unanticipated cracks, even when all of these techniques are used together, always arise. Still, they're like deadbolt locks, car alarms, and other security measures: tools that provide enough protection to encourage the bad guys to go elsewhere.
Online privacy technique No. 1: Cookie management
The search engines and advertising companies that track our moves online argue they have our best interests at heart. While not boring us with the wrong ads may be a noble goal, that doesn't mean the relentless tracking of our online activities won't be used for the wrong reasons by insiders or websites with less esteemed ideals.
The standard mechanism for online tracking is to store cookies in your browser. Every time you return to a website, your browser silently sends the cookies back to the server, which then links you with your previous visits. These little bits of personalized information stick around for a long time unless you program your browser to delete them.
Most browsers have adequate tools for paging through cookies, reading their values, and deleting specific cookies. Cleaning these out from time to time can be helpful, although the ad companies have grown quite good at putting out new cookies and linking the new results with the old. Close 'n Forget, a Firefox extension, deletes all cookies when you close the tab associated with a site.
Standard cookies are just the beginning. Some ad companies have worked hard on burrowing deeper into the operating system. The Firefox extension BetterPrivacy, for example, will nab the "supercookies" stored by the Flash plug-in. The standard browser interface doesn't know that these supercookies are there, and you can delete them only with an extension like this or by working directly with the Flash plug-in.
There are still other tricks for sticking information in a local computer. Ghostery, another Firefox extension, watches the data coming from a website, flags some of the most common techniques (like installing single-pixel images), and lets you reverse the effects.
Online privacy technique No. 2: Tor
One of the simplest ways to track your machine is through your IP address, the number the Internet uses like a phone number so that your requests for data can find their way back to your machine. IP addresses can change on some systems, but they're often fairly static, allowing malware to track your usage.
One well-known tool for avoiding this type of tracking is called Tor, an acronym for "The Onion Router." The project, developed by the Office of Naval Research, creates a self-healing, encrypted supernetwork on top of the Internet. When your machine starts up a connection, the Tor network plots a path through N different intermediate nodes in the Tor subnet. Your requests for Web pages follow this path through the N nodes. The requests are encrypted N times, and each node along the path strips off a layer of encryption like an onion with each hop through the network.