Absolute anonymity is not practical, in real life or on the Web.
All human interaction involves exchanging data of some kind. If someone weaves enough of that data together, they can identify you. Think about all the information that a person can glean in just a short conversation with you. In one glance, they can gauge your height, weight, and approximate age. Your accent will probably tell them what country you are from, and may even tell them what region of the country. If you talk about anything other than the weather, you will probably tell them something about your family, your interests, where you live, and what you do for a living. It does not take long for someone to collect enough information to figure out who you are.
The same thing is true of the Internet. If you visit a website, the owner can, if sufficiently motivated, find out who you are. After all, the ones and zeroes that make up the Web session have to be able to find their way to the right place and that place is your computer. There are a lot of measures you can take to disguise the bits, and the more of them you use, the more thoroughly the bits will be disguised. For instance, you could use network address translation to mask your actual IP address, subscribe to an anonymizing service that launders the bits by relaying them from one end of the ether to the other, use a different ISP account for different purposes, surf certain sites only from public kiosks, and so on. All of these make it more difficult to determine who you are, but none of them make it impossible. Do you know for certain who operates the anonymizing service? Maybe it is the same person who owns the website you just visited! Or what about that innocuous website you visited yesterday, that offered to mail you a free $10 off coupon? Maybe the owner is willing to share information with other website owners. If so, the second website owner may be able to correlate the information from the two sites and determine who you are.
Does this mean that privacy on the Web is a lost cause? Not at all. What it means is that the best way to protect your privacy on the Internet is the same as the way you protect your privacy in normal life, through your behaviour. Read the privacy statements on the websites you visit, and only do business with ones whose practices you agree with. Most importantly, avoid indiscriminate Web surfing. Recognize that just as most cities have a bad side of town, the Internet does too.
Computer and Communications Systems Manager | Medicine | Psychiatry
The University of British Columbia | Pt. Grey Campus
Phone 604 822 7374