Super User is a question and answer site for computer enthusiasts and power users. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

Just recently I've noticed from my Comodo Firewall that I have strange outbound connections when using Firefox. It keeps secretly downloading nothing. Every time I download any type of file I get strange ports using my bandwidth and not sure what its using it for. I blocked all of the unknown IP Addresses the first time and still could search the internet and do everything else normally. But eventually new ones will pop up again.

This may have been going on for a while (2 years!) but I was able to find out because of the new Comodo. My downloads are 30kb if Firefox connections are left alone when normally it would be without it 250 to 400kb before it came to this point. That's when I noticed the strange connections and after blocking them my bandwidth jumped per download to 750-800kb!

I'm happy but this is tedious because new addresses keep popping up and I have to keep blocking them. What is going on? Anyone else have this problem? Is there a better way to defend against this?

Thank you!

share|improve this question
up vote 3 down vote accepted

It may be plugins or addons to Firefox performing some type of background downloading. I would start Firefox in safe mode and then try downloading to see if things persist.

"Strange ports" - do you mean strange source ports (which are normal to be random) or strange destination ports? The destination ports are normally going to be more helpful in identifying what is going on.

You may also look for an online whois tool (there's many) and run a few of the addresses through them to see if that leads to anything interesting.

share|improve this answer
The Destination is what I meant. I ran safe mode and also disabled my add-ons one by one. At first it seemed like it was working after disabling add-ons I believed were downloading but now the problem still persist after doing the latter. – superduperuser Feb 26 '12 at 14:22
You may have some type of local proxy server running on your system, either through malware or some security/antivirus software (likely the former). – LawrenceC Feb 26 '12 at 16:50
The local proxy server is possible as I have installed 3 Firefox Add-ons for Proxy use but have uninstalled them. I really don't know where to look for that one. I also have Comodo running their DNS Server so I will turn that all and research more on it. – superduperuser Feb 27 '12 at 10:49
The issue is one of my plugins, not my addons. I thought they both were the same thing but now I know what your talking about. I disabled all of them accept for Flash Player and its no longer downloading secretly. I can find out the problem from this point. Thank you for the help. – superduperuser Feb 28 '12 at 12:54

Firefox is probably updating itself, updating its addons, or downloading fresh antiphishing data (list of blacklisted domains).

Also some addons may download additional data (e.g. AdBlock may update its lists of filtering rules).

So, in order to save bandwidth, you have to disable firefox/addons autoupdates, antiphishing, and some plugins. Looks like bad idea from security perspective.

share|improve this answer

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .