Comodos free Firewall is your first layer of defense against viruses, malware, worms, Trojans, hackers, and all Internet threats. In order to prevent threats from occurring, rather than just detecting them when its already too late, Comodos Firewall utilizes unique Default Deny Protection. When a file or application knocks on your PCs door, Comodo Firewall is able to access a safe list of over 2 million files and applications that are known to be PC-friendly. If the file asking for access is on the list, Comodo Firewall can be sure its safe for your computer and allow it to execute.