Comodo Firewall

Comodo's free Firewall is your first layer of defense against viruses, worms, Trojans, hackers and all Internet threats.

Comodo's Firewall uses Default Deny Protection to prevent threats from occurring, rather than just detecting them when it's already too late. Whenever an unknown piece of software is introduced to your system, Comodo Firewall cross-references it with a white-list of over 15 million trusted files and applications. If the file asking for access is on the list, Comodo Firewall can be sure it's safe for your computer to allow it to execute. If not, Comodo Firewall will alert you that a possibly malicious file is trying to enter your PC. The latest version sees a major leap forward in security and usability with the addition of cloud based scanning and behavior analysis of unrecognized files - making Comodo Firewall unbeatable at detecting zero-day attacks.