A large number of commercial companies now track users' browsing across the web, in order to profile them, and then serve them targeted advertising. This so called behavioral advertising is a threat to the average user's privacy.
An industry group, The Network Advertising Initiative, provides an easy way for users to opt-out of the tracking performed by its member companies. Users can visit a single web page, and then easily set opt-out web cookies for all of the NAI members advertising networks.
The problem with this is that the moment a user clears his or her cookies, they also lose the opt-out cookies. Regularly clearing browser cookies, or better, setting the browser to erase them all at the end of a session, is a recommended practice. Unfortunately, by doing this, users are then required to re-visit the NAI opt-out page each time they start browsing the web. This is obviously not a reasonable thing to expect.
Google recently announced that it would be engaging in the large scale collection and use of targeted advertising information. However, in addition to offering an opt-out cookie, the company has also developed a Firefox add-on, so that users can maintain the opt-out cookies, even if they regularly erase the other cookies.
Google should be commended for releasing such a useful privacy enhancing technology (even though their use of targeted advertising is creepy, and should be prohibited by the FTC). If only this add-on could be used to protect people from the prying eyes of the other advertising networks.
Since Google released the Firefox-addon as an open-source project (under the Apache 2.0 license), I have forked the code, and added in the opt-out cookies of 16 other advertising networks.
By installing this add-on, you will receive long-term opt-out cookies for the following NAI member advertising networks:
- Google / Doubleclick
- Collective Media
- Next Action
- Audience Science
- Fox Audience Network
- Tacoda Audience Networks
- Traffic Marketplace
- Tribal Fusion
- Undertone Networks
The Bad News
All of the above companies use a cookie similar to "OPT_OUT=1". Unfortunately, some other NAI member companies force a unique tracking ID upon users in the process of opting out of the targeted ad tracking. That is, in addition to an "OPT_OUT=1", they'll also force a "USER=12345678" cookie, which could enable them to uniquely track visitors to their site.
For example, when trying to opt out of Yahoo's tracking, I was given the cookie
Similarly, Akamai gave me this cookie
Simply put, we shouldn't have to trust these companies to not track us. Users should not be given unique IDs in order to opt-out.
The following companies force unique IDs upon users wishing to opt-out. This add-on does not currently provide opt-out functionality for these networks, since I don't want to encourage their sketchy ways. Hopefully, being listed here might shame them into providing a more pro-privacy way of opting out.
These companies are:
- Blue Kai
- MindSet Media
- Media 6 Degrees
- 24/7 Real Media
- Specific Media
Disclaimer: This code is based on the Advertising Cookie Opt Out Plugin by Valentin Gheorghita, a Google Engineer. It was not sanctioned by Google, the Network Advertising Initiative. While the folks at the Berkman Center (who pay me) are huge supporters of privacy, I have done this in my personal capacity, and this is not an official blessed Berkman project.