A paper by researchers at Berkeley discussing Flash cookies, including Quantcast’s use of them, has received recent press attention highlighting the potential to reinstate browser cookies based on Flash Stored Objects (FSOs – a Flash based cookie).
Quantcast has always focused on delivering the most accurate audience measurement to our customers and as we’ve introduced new capabilities such as Flash measurement we’ve attempted to keep our measurement processes synchronized and as accurate as possible. One side effect of this synchronization is that a deleted browser cookie could be set to match the FSO, resulting in the reinstatement of a previously deleted cookie value.
We immediately took steps to remedy the behavior and have altered the process by which browser cookies and FSOs are set. We have confirmed with the Berkeley researchers that the restoration behavior no longer occurs.
As is required of our MRC accreditation process we are inspecting all measurement data carefully to understand and quantify any impact that this change would have on our audience measurement and reporting processes.
It should be noted that Quantcast uses Flash cookies for measurement purposes only and not for any form of targeted content delivery. Delivery opt-out, both directly here on the Quantcast site and on the Networked Advertising Initiative site has remained in full effect throughout and is neither impacted by our previous configuration or by the changes we have recently made.