If you are concerned about your online life being tracked through cookies, you should be thinking no only about regular cookies, but also Flash cookies, which are very common these days. Many, many web sites now use Flash, and much of it will leave cookies on your machine. In some cases, the Flash is there for no reason other than to leave tracking cookies on your machine, and has no visible effect at all on the appearance or behavior of the page that contains it. There might be no apparent sign that the site even uses Flash (there is, or used to be, some of this “tracking Flash” on the main Straight Dope site, on some of the columns by Cecil and the SBSAB). Flash cookies are a different sort of file from “regular” cookies, they hide in a different place on your hard drive, and they are not blocked or cleared by regular anti-cookie software such as Firefox or other browser’s security or privacy settings or (I believe) McAfee. Clearing your browser’s cookies, or its “recent history” will not get rid of them, and browsing in “private mode” will not stop them being created and left permanently on your hard drive. Presumably it is because ways to eliminate regular cookies are now so well known and readily available that many of the people who want to be able to track your online behavior now do it with Flash cookies instead.
To deal with Flash cookies, I recommend three Firefox add-ons:
[li]Flashblock stops any Flash from running unless you give it your explicit permission (which only takes one click). If it does not run, it can’t leave a Flash cookie either. On the other hand, if yo want to use a Flash dependent item, such as a YouTube video, it only takes one extra click to get it to run normally. You can whitelist any sites where you do want the Flash to play automatically.[/li]
[li]Nuke Anything Enhanced allows you to remove almost any item that you want from a web page. (Actually, it does not have to be “enhanced”, you can “nuke” a block of text if you want to.) This is valuable in its own right (in my opinion, if you have both this and Flashblock, you really don’t need Adblock), but it is really rather necessary if you have Flashblock because sometimes you find Flash items that block the content behind. These are the things that usually cause those animated ads that move across a web page. Flashblock stops them from displaying or running, but it does not remove them altogether in case they turn out to be a Flash item that you want. Unfortunately, this means that you cant click any links (or whatever) behind the Flash object without causing it to run. The way to get around this is to use Nuke Anything Enhanced (which works via right-click) to remove the offending Flash object altogether. (It is a bit hard to explain this issue clearly in words, but try out the add-ons and it should all make sense.)[/li]
[li]The Better Privacy add-on will clear any Flash cookies off your computer at the end of each browsing session. It basically does what the Firefox privacy controls enable you to do to get rid of “normal” cookies. Also, if there any sites whose Flash cookies you want to keep (if you want to keep your settings for Flash videos, for example), then you can whitelist them, and Better Privacy will not wipe their cookies (not all cookies are used for tracking, after all, though many are).[/li][/ul]