Microsoft has revealed a new feature that will ship with Internet Explorer 9 to help users avoid the online tracking that is now widespread on the Web and is used to power behavioral advertising. The new Tracking Protection Lists will tell the browser which third-party content to permit and which to prohibit.

Tracking Protection Lists will be an opt-in feature, and Microsoft says that it will not provide any lists itself. Instead, third parties can provide lists to end-users. As such, the lists may come from privacy advocacy groups, ad-blocking advocates, or individuals who want to block certain content. The lists will update themselves automatically on a weekly basis.

Internet Explorer already contains a feature, InPrivate Filtering, that attempts to block third-party scripting and tracking devices. However, InPrivate Filtering operates on a heuristic basis. It can both fail to block certain tracking devices, and it can also block too much third-party scripting, leaving sites inoperative. Tracking Protection Lists, in contrast, will be curated, and so should be less susceptible to these issues.

The announcement comes not long after the FTC called for browser vendors to include a "do not track" button in order to block any kind of third-party usage tracking. Tracking Protection Lists would potentially be a finer-grained equivalent, allowing users to opt out of some or all tracking systems depending on their preferences. The lists might also be useful to prevent the kind of spying that YouPorn is being sued for.

Specifics of the Tracking Protection Lists are not yet finalized. Microsoft has proposed a file format for the lists, and it promises that the final specification will be available under a Creative Commons Attribution license.

Support for Tracking Protection Lists will first arrive in a release candidate of Internet Explorer 9. Redmond did not give a date for this, but it is likely to be early next year.