That has left consumers who don't want to be tracked with a more drastic option: Turn on the third-party cookie blocking setting in the browser and install special browser add-on software that prevents tracking scripts from running (because not all tracking is cookie-based).
It's not a complete solution, however. Anti-tracking tools defend against tracking only by third-party advertising networks that deliver ads through the content publisher's website -- although the tools do block all third-party requests, whether from ad networks, social media or analytics companies. The tools don't prevent any tracking by a "first party" -- the publisher of the site or any affiliated advertising networks it owns.
Replacing the cookie
While cookies assign a unique identifier to a user's browser, they can't easily be used to track the user's activity across different devices or even across different browsers running on the same computer. New techniques, such as those recently disclosed by Facebook, Google and Microsoft, will assign a unique identifier to each type of device the user has and link those together to track activity across all of the devices the person uses. These new tracking mechanisms, if they catch on, could be used across each vendor's ecosystem -- and beyond.
Other advertising networks have also been working with statistical identification methods -- browser and device "fingerprinting" techniques -- that don't require the presence of a cookie file.
Meanwhile, as user awareness has increased, so has the level of discomfort with the idea of having all of one's online browsing activity recorded -- particularly by third-party advertising networks that consumers don't know and with whom they have no relationship.
And as the number of tracking scripts has increased, so has the bandwidth consumed when the user attempts to load the page. "Up to 26% of bandwidth goes to loading trackers," says Sarah Downey, privacy advisor at Abine, the distributor of a free anti-tracking add-on program called DoNotTrackMe. According to Downey, the percentage comes from a 2012 Web crawling exercise conducted by Abine.
"As the industry moves toward stealthier methods of tracking [such as device and browser fingerprinting], the only way we can reliably prevent tracking is to block entire requests," says Brian Kennish, co-CEO of Disconnect. Tools like Disconnect take the draconian step of blocking requests to third-party ad networks to deliver an ad when the user visits the site -- which means even a non-targeted ad can't be delivered to the user.
In contrast, a universally accepted Do Not Track mechanism would still allow third-party advertising networks to substitute a contextually appropriate ad for a behaviorally targeted one (e.g., a game ad for users on a gaming site) rather than cutting off the request entirely. "We'd prefer a more subtle solution where we don't have to throw out the entire request," Kennish says.
"It's a very blunt tool. That's why we're trying to find a middle ground with Do Not Track," says the Center for Democracy and Technology's Brookman.