Cookies are small text files sent to your PC by servers at the websites you visit. They get their name from “magic cookies” in Unix, which are short data communications between two programs where the second program, the one receiving the cookie, may not even be aware of the content of the message.
In a similar way, web browser users are not usually aware of the content of the message in a cookie.
By convention, cookies are only sent from your computer to the domains that set them. An organization like Google or Yahoo, for example, would have many different destinations within
their domain. Thus, many locations within the domain could interact with the cookie.
When you visit a website, you may encounter a graphic or other page element that actually isn’t part of the page. Instead, it’s served from a remote server. Your browser, in the act of connecting to that other location, gives that server access to their cookie.
An advertiser may recognize that cookie, identify you by habit (or name, if you’ve entered your name at some website within their sphere) and then decide what advertising to send to that page. All this happens as the page loads. This type of cookie is called a third-party tracking cookie. Generally, any cookie that does not originate in the domain you’re visiting is a third-party cookie. The advertiser would say that they are targeting ads that will likely appeal to you.
It doesn’t have to be a graphic, video, music link, or anything that you’ll recognize, either. It can be a single pixel in the corner of the page. These are called “web bugs.” A web bug may do nothing other than tell the advertiser, “He was here.”
Now multiply that by a million websites. A company that also sells ads would have a big incentive to make carrying their ads dependent on also carrying their tracking and targeting applications. This is called analytics.
Let’s look at getting rid of them.
In Internet Explorer 7, press Alt to bring up the menu, and click on Tools. Then click Internet Options. Slide the Privacy slider to the middle or higher.
At this level, IE “blocks third-party cookies that do not have a compact privacy policy.”
This is what W3C (an internet standards organization) has to say: The Platform for Privacy Preferences Project (P3P) enables Websites to express their privacy practices in a standard format that can be retrieved automatically and interpreted easily by user agents. P3P user agents will allow users to be informed of site practices (in both machine-
and human-readable formats) and to automate decision-making based on these practices when appropriate. Thus users need not read the privacy policies at every site they visit.
In Internet Explorer 7, even “High” allows cookies from websites with a compact privacy (P3P) policy. You’d have to block all cookies in order to block these.