In case anyone isn't familiar with recent events, some people discovered that the installation of avast 7 interfered with the operation of their firewall and prevented their firewall from blocking traffic in the way they desired and expected. Based on my casual wanderings and readings (which have included the Comodo forum thread http://forums.comodo.com/firewall-help-cis/comodo-firewall-and-avast-7-t82382.0.html ) I believe the problem scenarios discovered thus far are: Windows 7 + Comodo Firewall + avast7 Windows 7 + Private Firewall + avast7 Windows 7 + Windows Firewall + avast7 A post from yesterday suggests there may be at least one more: Windows 7 + Windows Firewall + avast6 I think this a case of avast manifesting a pre-existing shortcoming in the way certain firewalls selectively block traffic on some operating systems such Windows 7. Avast hooks the networking stack to put its Web Shield in the position of a local proxy so that it can inspect and block traffic on some web related ports. It appears that some firewalls may not have enough visibility or control over things to cope with that local proxying. Since there could be other software programs that establish a local proxy in way similar to that used by avast and perhaps even other firewall/OS combinations that have shortcomings, I thought I'd post this.