Turn Off 3rd Party Cookies in Firefox 2.0

If you casually surf the web, 3rd party cookies are a privacy problem. Advertisers like DoubleClick use them not only to profile where you've been, but what you've been doing. Many people don't know that advertisers and other ne'er-do-wells can capture very specific user data, like words that you've searched for in popular search engines. In Firefox 1.x, it was easy to go to Preferences (OSX) or Options (Windows) go to Privicy, click the Cookies tab, go to "Allow site to set cookies" and check "for originating site only".

This convenient option is gone in the Privacy settings in Firefox 2.0. You can still block most 3rd party cookies by editing the configuration file. Just type "about:config" into your address bar and hit return to open it and then type cookies into the filter at the top. The line you want to change is "network.cookie.cookieBehavior". In the Value column, the default value is set to "0" which basically means "Accept All Cookies" as detailed in this knowledge base article. Click on "0" and change it to "1" which translates into "Only Accept Cookies From The Site I'm Visiting" and hit return. That's it, you're done!

For more information on this and other security topics, check out epsiode 64 of "Security Now" at Steve Gibson's excellent GRC.com.