14 DAY TRIAL // A student fellow at Harvard University has developed an extension for the Mozilla Firefox browser, which allows privacy-concerned Internet users to protect themselves from behavioral targeting. It is currently able to set permanent opt-out cookies for 27 advertising networks that track browsing habits.
Targeted advertising is a concept that involves only serving advertisements to a user that might be of particular interest to them. The most widely-used technique at the moment is called "contextual advertising" and implies serving ads according to the content of the Web page that they are viewing.
This is based on the idea that the user is interested in the content that is displayed to them at that particular moment, but obviously, this might not always be the case. In addition, the algorithms employed to determine what the content is about are far from perfect.
Therefore, advertisers have come up with a better way of assessing the interests of the users, based on their behavior. This is called "behavioral targeting" and involves tracking and analyzing browsing habits, purchase a search history, as well as their location. However, while this technique might, indeed, improve the relevancy of the ads and result in better consumer interest, it poses significant privacy issues.
Faced with pressure from Internet privacy groups and other organizations, the advertising networks engaging in such practices have started offering users the option to opt-out of having their online habits tracked. This comes in the form of a browser cookie, which tells the advertising mechanisms not to analyze the behavior of the consumer.
Christopher Soghoian, a student fellow at the Berkman Center for Internet & Society at Harvard University and developer of the Targeted Advertising Cookie Opt-Out (TACO) Firefox extension, explains why browser cookies are not the best way to achieve this. First of all, clearing cookies is a common practice and, from a security perspective, a recommended one. Because of this, most browsers offer an option to automatically remove them after each browsing session.
This means that the user would need to manually set their opt-out cookies again every time they are cleared. "This is obviously not a reasonable thing to expect," Mr. Soghoian writes, as, in addition to Google or other well-known online advertising networks, there are tens of other agencies that the average users are not aware of.
Google has tackled the issue of cookies-clearing by developing its own open-source Firefox extension that has the simple purpose of automatically restoring its "opt-out of behavior tracking" cookie. Mr. Soghoian has extended Google's tool and has added similar cookies for 26 other advertising networks.
The TACO extension actually installs 41 such opt-out text files in the browser, because some networks operate several different domain names and cookies are domain-based. "Clearing your browser cookies will not delete these opt-out cookies. The only way to do that is to remove the add-on and then clear your browser cookies as normal," the Harvard fellow notes.
However, while this add-on will significantly increase a user's privacy, it is not by far perfect. This is because some networks use cookies that contain unique identifiers, ironically to track those who don't want to be tracked. These IDs are not something that this extension can determine in advance, and therefore will not protect them from the habit-tracking practices of several advertising services, including Live.com (Microsoft), Yahoo! or Akamai.
Soghoian suggests that a better approach to opting out would be to include a setting in the HTTP-header being sent by the browsers that marketers would agree to honor. But this would imply the major browser vendors sitting down and developing a common specification, and if that happens, it is likely that the option be enabled by default, the academic maintains.
"If the browsers included such an opt-out header turned on by default, it would transform the targeted Web advertising business from an opt-out system into something that would effectively be opt-in for most users, which is a scenario that the advertising networks, Google included, desperately want to avoid," Christopher Soghoian writes. "In the mean time, we're stuck with this pretty useless status quo," he concludes.
You can download the TACO extension from Mozilla's repository (free developer account required until it has been approved by Mozilla) or directly from Christopher Soghoian's website.