That's good. The interesting question would be: why? a) Blocked because Windows7FirewallControl see's Firefox attempting to connect to a remote host? b) Blocked because Windows7FirewallControl sees Firefox attempting to connect to local port 12080 (after the Avast redirect)? c) Blocked because Windows7FirewallControl is blocking Firefox's other use of local ports? I think the desired behavior would be for everything to be blocked. The "it depends" part is curious. As you probably know, Avast doesn't redirect HTTPS connections to the local proxy. So if the sites that are working are, for whatever reason, being fetched via HTTPS it might make sense. Regarding the localhost stuff, it sounds like domain guessing (browser.fixup.* config settings) is coming into play. If you ever want to you can disable that and/or go the pretend-to-be-a-browser route via telnet. Thank you very much for testing and sharing info. It is interesting that Windows7FirewallControl is doing at least some blocking that some other firewalls aren't. If Comodo doesn't address this issue on Win7 via their newer version, I may take a look at it myself.