Flash cookies are also known as Flash LSOs or Local Shared Objects. They are a type of browser cookie that can be placed on your computer by Adobe Flash Player. Like regular cookies, Flash Cookies cannot be removed through common Internet browsers such as Chrome, Firefox, and Internet Explorer.
Flash cookies were designed to store information about your visit to a website so that it can remember things like your user name, preferred language, and other preferences. While they may not be useful for storing sensitive data like credit card numbers or Social Security numbers, they could still pose a privacy risk because they allow websites to track your online activity across multiple visits.
Flash cookies can be used to target ads based on previous interests and preferences, but some people find this invasive and annoying. In response to this concern, Google Chrome has blocked Flash cookies since August 2011 by default (although you can still turn them on if you choose).