What does Google Know about You?
What does Google Know about You?
Rumors swirl around the topic of online privacy. Some Internet users wish to be completely anonymous, some don't know who's watching and couldn't care less. Regardless of your desire for privacy, you should have some idea what your potential for exposure might be. If you are an AdSense publisher, this information is crucial to your understanding of how you might make money or possibly get shut down by Google deities.
Start with a Cookie
It all starts with a cookie. Generally, any web site you visit may leave one or more cookies on your computer. The web site may store information such as the time/date of your visit, how long you stayed, what pages you browsed, and even private information. Your login ID and password (for the specific site, not for your computer) may be encoded into the cookie as well. Some sites may even save credit card information, but generally information that sensitive is either stored on the company computer or not stored all.
Some sites are even more sophisticated. The cookie they store contains only a unique identifier; everything else is stored on the company server. Anytime you visit the site, your browser sends the contents of the cookie to the web server. Any activity is recorded in a database on the 'server side' in a file that is associated with your unique identifier. Information accumulates under your identifier. You have no control whatsoever over the disposition of the collected data. It may persist for many years, being transferred to any number of databases for any imaginable purpose. Any information you provide to the site may become part of your file.
You can delete your cookie. You can't delete the information stored at the other end. You can also block cookies through your browser. All browsers support blocking all cookies; some browsers also support blocking cookies from specific domains.
Should you Block Cookies?
Blocking cookies is a two-edged sword. On one hand you can eliminate many ads by blocking a handful of domains. On the other hand, blocking all cookies will severely limit your browsing experience. Some sites will alert you if they can't leave a cookie. Some sites simply behave erratically without crucial cookie data.
For example, Google.com insists on a cookie before allowing you to configure your Advanced Search settings. Block the Google cookie and you Google will block you from http://www.google.com/advanced_search. Google also requires access to its' cookie when checking your adsense earnings.
You don't have to Visit a Site to get a Cookie
Cookies accumulate faster than you might think. Surf to Yahoo.com. You will receive at least one cookie, but probably three or more. Technically you have just visited more than one site. Each company that places an ad on the Yahoo home page will also leave a cookie. The ads originate from a domain other than Yahoo.com. For example, DoubleClick.net serves ads to Yahoo pages. This company leaves a cookie on your computer when you visit Yahoo.com because your browser is also connecting to DoubleClick.net in order to download the advertisement. Every time you visit any other site that is served by DoubleClick.net, the contents of their cookie is returned to them. Your browser sends it automagically, without your knowledge.
Interestingly enough, Google owns DoubleClick.net.
The Good News
No site can read the cookie left by any other site. Yahoo can't read the Google cookie and DoubleClick.net can't read the Amazon.com cookie. However. there's no restriction on servers sharing information from cookies after that information has been (voluntarily) transferred to them by your browser. Rest assured that advertising aggregators apply information collected from cookies to develop sophisticated selling campaigns.
Connecting the Dots
Anytime you visit a site that publishes AdSense content, Google knows about it. They may know more than you imagine. Given that Google has long since stored a cookie on your computer, Google servers receive that cookie from your browser each time you visit Google.com. They assigned you a unique identifier, which is stored in the cookie and is tied to your Google account (for example, my Google account is my Gmail address and password) if you have one.
Note: If you have not identified yourself to Google, all they have is the unique identifier in your cookie. They may still use that to track your online behavior, but the information gathered will not be tied to your name.
A Simple and Powerful Experiment
Caution: This will delete all your cookies. Make sure you understand the ramifications.
- FireFox 3.5.3 under Windows is assumed...
- Close your browser and reopen it
- Click Tools / Clear Recent History
- Under "Time Range to Clear" select Everything
- Under Details, uncheck all the options except cookies
- Click Clear Now and confirm the operation if prompted.
- Close the Clear Recent History window if it's still open. Leave FireFox open.
- Browse to Yahoo.com
- Click Tools / Options / Privacy / Show Cookies. Note the cookies that have accumulated from browsing to Yahoo.com. You will probably see three or four cookies; one from Yahoo.com and several others from advertisers who published on Yahoo.com
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