Many people know that a quick trip to their browser’s Preferences panel can allow them to disable somebody’s ability to track online activity using regular old Web cookies. However, these new Flash cookies use Adobe’s Flash plug-in to sneak in and do their dirty work. And in most cases, no browser setting can touch them. To turn these off, go to the Web page for the Adobe Flash Player Settings Manager (do a search for those words), click the tab for the Global Storage Settings panel and uncheck the box labelled “Allow third-party Flash content to store data on your computer”.

But to your next question: unlike regular Web cookies, which need to be turned off on every browser you use, changing the Flash cookies setting on one browser should carry over to other browsers on the same computer.