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Your browser has to ask Web sites to send files to your computer. So that site knows your address unless you use a firewall.
 technofile
Al Fasoldt's reviews and commentaries, continuously available online since 1983

T e c h n o f i l e
Why your browser gives away your privacy, and other Web secrets


June 20, 2004


By Al Fasoldt
Copyright © 2004, Al Fasoldt
Copyright © 2004, The Post-Standard

   The least understood part of the Internet is the part many of us use most. It's the World Wide Web. In most cases, just about everything we know about the Web is wrong.
   And that's surely the main reason we're so careless about our Web-browsing habits. After all, if we knew we were playing with fire, we would keep sparks at a safe distance.
   Let's start with a quick quiz. See if you can answer these three questions correctly:
   1. When your Web browser goes to a Web site to show you a page, it takes whatever files are needed to show the contents of the page and copies them across the Internet. True or false?
   2. The links on Web pages are always safe. You can click on them without worry. It's the links in e-mail messages that are unsafe. True or false?
   3. There are many different kinds of links. Some kinds are used by spammers and others are used only by Google and other search sites. True or false?
   Ready to grade yourself? If you answered "true" to any of the questions, you got that question wrong. All three questions were false.
   Let's see why.
   1. Web browsers never take files from a Web site. The World Wide Web won't let this happen. Browsers have to ask the server computer (the one hosting the Web site) to send them the files that make up the page they want to open. The server computer asks the browser for its IP (Internet Protocol) address and then sends the file to that IP address.
   During the brief transaction that takes place, the server computer writes down your browser's address. It literally knows where you are, at least in Internet addressing terms. (It knows how to find you again if it has to, even if it doesn't know your computer's actual street address.)
   The fact that your browser has to ask Web sites to send it files means you have no privacy unless you can hide your address behind some kind of clever smokescreen. Fortunately, that's just what most firewalls do. Firewalls tell white lies about where you are. But if you're not using a firewall on your Windows PC, Macintosh or Linux computer, or if you're not using a separate firewall device (usually combined with a router) connected to your cable or DSL modem, you are advertising your Internet address to every Web site. You have no chance of privacy without a firewall.
   2. Links on Web pages are HTML launchers. They send your Web browser to Web sites to do whatever the link says it should do. Links in e-mail messages are ... ready for this? ... HTML launchers. They send your Web browser to Web sites to do whatever the link says it should do.
   There's no difference between links in Web pages and links in e-mail. They're both potentially dangerous.
   3. You should have figured out this answer by now. Links are links. Spammers can use any links they want, and they can make them look like missives from the Pope or requests from your friend Cindy to look at her prom pictures.
   If you got all the answers right, congratulations. But here's a tie breaker on Internet safety in general.
   Bonus: If you click on a link in an e-mail message to be "taken off the mailing list," you're doing yourself a big favor. The ever-friendly spammers will happily remove you from the list. True or false?
   The answer, as many of you already know, is that spammers aren't friendly and helpful at all. They'll remove your name from the list that brought you that piece of spam, alright. After all, it's a blind list, sent to millions of addresses in hopes of turning up a few thousand that are legitimate. Then they'll put your address on a confirmed list. And you'll be flooded with even more spam as a result.