# Using Privacy Features

The Internet is a public network of millions of computers, all sharing information. On the Internet, information moves back and forth across public lines and through numerous connections. As with all public lines, eavesdropping is possible.

Fortunately, your browser contains features that safeguard your privacy. In addition to the information in this document, you can always find the latest news about security at Netscape's Security Center. For more information about privacy and security, including information about viruses, secure email, safe online shopping and banking, and safe surfing for children, see Understanding Security, a document located at the Security Center.

For background information about privacy on the Internet, click the first topic below. For instructions on using specific browser features that help protect your privacy, click the topic for the feature you want to use.

Privacy Topics: Privacy on the Internet Using the Cookie Manager Using the Password Manager Using the Form Manager Encrypting Stored Sensitive Information Managing Images Privacy & Security Preferences

# Privacy on the Internet

This section summarizes some background information about privacy on the Internet. It also describes several things you can do to safeguard your own privacy.

For a more detailed discussion of privacy issues, see the Privacy Tutorial.

In this section: How Does a Web Site Gather Information About Me? What Information Does My Browser Give to a Web Site? What Are Cookies, and How Do They Work? How Do I Make Sure Unauthorized People Don't Use Information About Me? Browsing Anonymously

## How Does a Web Site Gather Information About Me?

There are two ways that a site can obtain information about you:

- When you request to view a page from a site, a certain amount of information is disclosed in the page request that your browser makes on your behalf.

- If you fill out and submit an online form, the information you filled in is sent to the site.

There are two ways for sites to store information about you:

- While your browser is getting a page from a web site, the site could ask your browser to store a small amount of information about you on your own hard disk. This stored information is called a "cookie." A site that stores (or "sets") a cookie will ask your browser to let it read the cookie the next time you visit.

- Any information you give a web site (by filling out an online form) could be stored on the web site's computers.

A web page can't find out your email address, name, or any other personal information unless you explicitly provide it. You are in control—no one can obtain personal information about you unless you allow it.

## What Information Does My Browser Give to a Web Site?

When you ask to view a web page from a site—which you do each time you click a link or type a URL—a small amount of information is given to the site. This information includes your operating environment, your Internet address (not your email address), and the page you're coming from.

Operating Environment

The site is told something about your operating environment, such as your browser type and operating system. This helps the site present the page in the best way for your screen. For example, the site might learn that you use the French version of a mozilla-based browser on a Windows 2000 computer.

Internet Address

Your browser must tell the site your Internet address (also known as the Internet Protocol, or IP address) so the site knows where to send the page you are requesting. The site can't present the page you want to see unless it knows your IP address.

Your IP address can be either temporary or fixed (static).

If you connect to the Internet through a standard modem that's attached to your phone line, then your Internet service provider (ISP) assigns you a temporary IP address each time you log on. You use the temporary IP address for the duration of your Internet session. Each ISP has many IP addresses, and they assign the addresses at random to users. A web site can tell which ISP a temporary IP address comes from, but it can't learn anything about you personally from your temporary IP address.

Important: Your IP address is not your email address. Your email address uniquely identifies you in cyberspace just as your social security number identifies you in the real world. A temporary IP address is no more a part of your identity than the phone number of a pay telephone you use to make a call.

If you have DSL, a cable modem, or a fiber-optic connection, you may have a fixed IP address that you use every time you connect.

Whether your IP address is temporary or fixed, you might not want that information to be given to a site you intend to visit. To block your IP address from being given out, see Browsing Anonymously.

Referring Page

The site is also told which page you were reading when you clicked a link to see one of the site's pages. This allows the site to know which site referred you. Or, as you traverse the site, it allows the site to know which of its pages you came from.

## What Are Cookies, and How Do They Work?

A cookie is a small bit of information used by some web sites. When you visit the site that uses cookies, the site might ask your browser to place one or more cookies on your hard disk.

Later, when you return to the site, your browser sends back the cookies that belong to the site.

By default, this activity is invisible to you, and you won't know when a site is setting a cookie or when your browser is sending a web site's cookie back. However, you can set your preferences so that you will be asked before a cookie is set.

### Why Permit Cookies?

There are times when it would be to your advantage to allow a site to know something about your previous visits. For example, if you were previously filling out a long form and got as far as page 17, it would be nice if the site could take you immediately to page 17 on your next visit.

### Why Reject Cookies?

If a site can store a cookie, it can keep track of everything you've done while visiting the site by writing these things into a cookie that it keeps updating. In this way, a site can build a profile on you.

This may be a good thing or a bad thing depending on what the site does with the information. For example, it might be good if a bookseller knew you frequently looked for information on dogs so it could tell you about a new dog book. It might be bad if the bookseller then sold that information to the local dog pound so they could cross-check for potential dog owners who do not have valid dog licenses.

### How Do Sites Use Cookie Information?

Web sites can use cookie information to tailor their presentations to you, and advertisers can use such information to target online ads to your interests and buying information. Reputable web sites have privacy policies that describe how they use the information they receive.

When in doubt, always check a web site's privacy policy before permitting a cookie to be set, and before providing any personal information (such as your name and email address).

### Encountering Foreign Cookies

If your browser stores a site's cookie, it will return the cookie only to that particular site. Your browser will not provide one site with cookies set by another. Since a web site can only receive its own cookies, it can keep track of your activities while you are at that site but not your activities in general while surfing the Web.

But suppose that while you visit site ABC.com, a cookie gets stored not by ABC.com but by a different site called XYZ.com. ABC.com can cause that to happen very simply by displaying an image from XYZ.com. So when you visit ABC.com your browser makes a side-trip to XYZ.com to get the image, and XYZ.com stores the cookie at that time.

If XYZ.com enlists many sites to display its cookie-storing image, it can build up a cookie that contains information about your behavior at all those sites. The more sites that display XYZ.com's image, the more encompassing a profile it can build on you.

Such cookies that are stored by the site other than the one that you think you are visiting are called foreign cookies. If you are concerned about foreign cookies but not about ordinary cookies, you could give permission for sites to store ordinary cookies only but not foreign ones.

You use Cookie Manager to specify what types of cookies you want your browser to accept.

## How Do I Make Sure Unauthorized People Don't Use Information About Me?

The best way to keep your information private is to be cautious about providing it to others. The Internet is a public network, and you should assume that when someone asks you for your name, phone number, address, and other information, they might share that information with others.

Providing your name, address, and phone number on the web is like having a listing in the telephone book. In fact, if you are listed in the white pages of the telephone book, your name, address, and phone number are probably listed in online directories and other databases on the World Wide Web. (Try looking yourself up in a directory such as People Finder or Yellow Pages.)

If a web site asks for information about you, always check the site's privacy policy before proceeding. Here are some questions you might ask about a web site's privacy policy:

- What kinds of personal information is this site gathering?
- How will the site use the information?
- Will the site share the information with others, for purposes unrelated to my dealing with the site?
- Can I access some or all of the information a site gathers about me, in order to inspect or update it?
- How does the site keep intruders from viewing the information?
- How do I contact the web site if I have questions or problems?

## Browsing Anonymously

When you request to see a page from a site, your browser must tell the site your Internet address (IP address) so the site knows where to send the page. Your IP address can be either temporary or fixed (static).

Whether your IP address is temporary or fixed, you might not want that information to be given to a site you intend to visit. But if your browser doesn't provide this information, the site won't know where to deliver the requested page. So this is the one piece of information that you can't ask your browser not to reveal.

If you really want to hide your IP address from the site, you need to use some trusted intermediate site. You go to the intermediate site and tell it the name of the site whose page you want. The intermediate site requests the page on your behalf, using its own IP address as the return address. Then, when it gets the page, it forwards it on to you. The site that supplied the page never sees your IP address.

There are several sites that provide such services. Use your favorite search engine to find them---try search words such as "anonymous" and "surfing".

[ Return to beginning of section ]

30 January 2002

Copyright © 1998-2002 The Mozilla Organization.