In August 2009, we demonstrated that popular websites were using “Flash cookies” to track users. Some advertisers had adopted this technology because it allowed persistent tracking even where users had taken steps to avoid web profiling. We also demonstrated “respawning” on top sites...

At UC Berkeley, we are informing political debates surrounding online privacy through empirical study of website behaviors. In 2009 and 2011, we surveyed top websites to determine how they were tracking consumers. We found that advertisers were using persistent tracking technologies that were...