The Wall Street Journal continues its in-depth report, “What They Know,” about the state of surveillance in the United States and how these surveillance programs affect individual privacy. In the latest installment, the Journal answers readers’ questions about technology and privacy.
If I delete all cookies and then later enable them, can the new cookies be associated with the “old” cookies? Does deleting cookies force trackers to start over, or do they just pick up where they left off, combining the new with the old?
When a consumer deletes all cookies from his computer and later enables them, tracking companies generally can’t associate the data from the “new” cookie with information from the “old” cookie, says Jules Polonetsky, director of Future of Privacy Forum, a Washington-based group that advocates “responsible data practices.” The group is supported by several online advertising companies, including AOL, eBay, Microsoft and Yahoo. […]
Some tracking companies can subvert this by using technology such as Adobe System Inc.’s Flash program. Flash cookies can be used to remember a particular user and re-install cookies that a user has deleted. The Network Advertising Initiative, an industry trade group, and Adobe condemn the practice. “That is certainly deceptive behavior, not something that acceptable folks do,” Mr. Polonetsky says.