You may think you're thwarting advertisers and other nosy web citizens by blocking cookies and invoking Do Not Track whenever possible, but that apparently isn't good enough. Researchers have just documented a newer web tracking technique, canvas fingerprinting, that's nearly impossible to stop. As it's simply drawing a unique, hidden image using standard web code, you can't just filter it out using higher privacy settings or ad blocking tools. You can sometimes opt out of personalization and targeted ads by installing a cookie, but you're otherwise out of luck unless software can start identifying and blocking these fingerprints. One of the earliest proponents of the technology has been the social sharing service AddThis, which started public fingerprint testing earlier this year. While you may not have heard of the company, there's a good chance that you've been to one of the sites that uses its tracking.