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Controlling Your Data



As we described in the Simple Behavioral Advertising section, most Web sites use cookies to track users on their sites. If you would rather not be tracked this way, you have a few options. You can:

  • Block cookies from first-party sites that are tracking you
  • Occasionally delete cookies from first-party sites that are tracking you


Blocking cookies from a particular site prevents that site from depositing new cookies on your computer and requesting old cookies that you already have. This provides good privacy protection, because it becomes impossible for the site to create a profile tied to a cookie that resides on your computer. One potential downside is that some sites may not function properly if your browser blocks their cookies. The best way to find out if this is the case is to try blocking the site’s cookies and see what happens. Also, if you want to create an account that stores your information and recognizes you when you return, you may have to accept cookies from that site. For information on blocking first-party cookies from particular sites, see GetNetWise. Here’s an example of the kinds of options that you have for cookies:

If the site you’re interacting with doesn’t work so well when you block cookies, then a better option may be to occasionally delete the cookies from that site. If you do this, it is much harder for the site to correlate your browsing behavior over time to any single cookie ID. For information on deleting your cookies.

If you’re looking to get even more granular with your cookie controls, all of the most popular Web browsers (and some browser plug-ins) offer additional cookie control features. Check out CDT’s report on browser privacy practices for more details on the differences between different browsers.

Behavioral advertising across multiple sites

Most behavioral advertising across multiple sites also relies on cookies. Your browser may have a special setting that allows you to automatically block third-party cookies. See GetNetWise and CDT’s report on browser privacy practices for more info.

Many anti-spyware products and other computer security products will also automatically block or delete third-party cookies. GetNetWise has more information to help you find the right security software for you.

Several ad networks provide you with a separate mechanism to opt out of their behavioral advertising. Unfortunately, these opt-outs are for the most part cookie-based – when you opt out, the ad network deposits a cookie on your computer indicating your choice. This means that in most cases if you ever delete that cookie, you will need to opt out again, You can opt out at the NAI site. Some companies have begun taking steps to make their users’ opt-out choices more persistent. See Microsoft and AOL for two fuller descriptions of how opt-out cookies are being made to last.

It’s important to understand that several ad networks allow you to opt out of receiving behavioral advertising, but they continue to collect data about your browsing behavior. To find out how a particular ad network responds to opt-out requests, it’s best to find and read the network’s privacy policy.

New targeting technologies

Most behavioral advertising still relies on cookies, but that doesn’t mean cookies are the only tool advertisers can use to track Internet users’ behavior. More and more of what you see on a single Web page is being delivered from multiple sources. Images, scripts of Web code, and "Flash cookies" may all be delivered by third parties, just as ads and cookies have been delivered by third parties for years. If these other kinds of objects are designed to be unique to an individual – that is, if the same object can uniquely identify a person across multiple Web sites – that opens up the possibility for them to be used for behavioral advertising.

Several makers of browsers and browser plug-ins are beginning to offer features that allow you to control which third-party objects can be stored on your computer. For more information, see CDT’s report on browser privacy practices, Microsoft’s description of the InPrivate Blocking feature in Internet Explorer 8, and EPIC’s guide to Flash cookies.

Other online privacy tools

There are numerous online privacy tools out there to help you safeguard your online experience. Many of these can help you control whether your data is collected for behavioral advertising by allowing you to surf the Web anonymously, encrypt your communications, or filter out Web sites that you don’t want to connect to. For an exhaustive list of online privacy tools, see GetNetWise or EPIC’s Online Guide to Practical Privacy Tools.

More information

Other sites with information on controlling your data with respect to behavioral advertising: