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Day of the Deleted - Quantcast Buries 'Undead' Cookies
Internet ratings firm Quantcast has stopped using a system which resurrects traditional browser cookies after users have deleted them.
A team of UC Berkeley researchers discovered 'undead' cookies created by Quantcast and others on Hulu.com; an online video site which uses Quantcast to measure its traffic.
The system makes use of cookies created by Adobe's Flash player, which collects information on how people navigate the millions of sites on which it is installed - information that is not erased when users clear cookies in the normal way. Quantcast was using the same user ID in its HTTP and Flash cookies, and when a user deleted the former, the firm would retrieve the Flash version from the storage bin and re-instate it.
According to the UC Berkeley study, that meant that 'privacy-sensitive consumers who 'toss' their HTTP cookies to prevent tracking or remain anonymous are still being uniquely identified online by advertising companies'.
The Obama Administration is currently considering whether to change its policy concerning the use of HTTP cookies on government web sites. Currently, government officials require a 'compelling need' to use persistent HTTP cookies, and must disclose their use in a privacy policy.
As part of their study, the researchers chose six government web sites to determine whether Flash was being used to assign unique values to visitors. Of the six sites they tested, three had Flash cookies and five used persistent HTTP cookies.
Last summer, Quantcast introduced an audience measurement solution which combines cookie-based traffic counts with people-based audience estimates for millions of its quantified web properties.
Web site: www.quantcast.com .
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