A recent endeavor at Stanford University’s Security Lab found more sobering information on the reach and capability currently employed by trackers such as Epic Marketplace (formerly known as Traffic Marketplace). The lab found that the scripts used on affected sites were very fast and loaded thousands of links in invisible iframes so few users would ever notice them. Whenever the browser window closed, the scripts sent off their findings and also stored their progress in scanning links with a cookie. In order to avoid having parallel scripts run concurrently and slowing down the process, some even used some semaphore-like cookies to start and stop. By scanning thousands of hidden links, these scripts could quickly develop a comprehensive history of browsing, and the lab found that these links ranged from eBay listings to health clinics, a serious privacy concern.