Tracking cookies are not viruses. Some sites use them to keep track of where you came from when you first visited the site, or to share information between sites. So it is a privacy concern. What you can do is make site Exceptions for cookies, and those deemed tracking cookies you make them "Allow for Session" or "Block". Those you want to make sure you don't lose like google you can mark as "Allow" those will override your choices for cookies. So the once you really want to control or allow are deleted or protected. Then you can change your defaults from one day to another. There is also private browsing ("Ctrl+Shift+"") that you can read about, if interested. My defaults under Tools > Options > Privacy     include :[x] Accept cookies from sites :     [x] Accept third-party cookies :     Keep until: they expire :[x] Clear History when Firefox closes -- under settings only cache will be cleared At the top of the Privacy options is :Tracking: [x] Tell web sites I do not want to be tracked :I guess it has been turned on for some time. But it does not carry much weight, it is not enforced by Firefox and a website is free to ignore, acknowledge, or act on it. If you have Adblock Plus you can install "Peter Lowe's List" subscription, it blocks tracking sites.