firefox phone home.jpgYesterday there was some concern raised over at Reddit because someone had noticed that both of Mozilla’s flagship products, Firefox and Thunderbird, call home every 24-hours. This happens regardless of whether you go into the Firefox preferences and disable all of the different types of updates. Why then does Mozilla’s products phone home then?

What happens is that the applications check with Mozilla on a daily basis to see if you’re running any extensions that Mozilla feels need to be blocked, whether it be because of stability or security reasons. A list of extensions that Mozilla is currently blocking can be found here, and at this time there are only five on the list:

  • Internet Download Manager, v2.1-3.3 for Firefox 3.0a1 and newer (see bug 382356).
  • Free Download Manager, v1.0-1.3.1 for Firefox 3.0a1 and newer (see bug 408445).
  • Yahoo Application State Plugin, v1.0.0.5 and older for Firefox 3.0a1 and newer (see bug 419127).
  • Vietnamese Language Pack, v2.0 for all applications (see bug 432406).
  • npLegitCheckPlugin.dll, for Firefox 3.0a1 and newer (see bug 423592).

I think the thing that caused the biggest stir is the fact that with each request Firefox also sends information including what version of the browser you’re using, what operating system you’re running, and other info that they can use to figure out how many active users they have.

This feature can be disabled by going through the about:config and searching for the extensions.blocklist.enabled option. If you set that value to false Firefox will stop phoning home, but you should probably think twice before doing this. A few years ago Mozilla created the block list as a way for them to centrally disable extensions if they are found to be malicious or cause instability in the browser. Remember the virus that modified the Vietnamese Language Pack? That’s exactly why it’s one of the five items currently blocked. If you disable this feature you could end up running an extension that you shouldn’t be.