So how affective is DefenseWall? To sum it up, if you have your "threat gates" untrusted/isolated, you can't be infected. "Threat gates" are programs such as browsers (Internet Explorer), mail clients (Outlook), and instant messengers (Windows Live Messenger); they all can receive malware or be exploited. And DefWall comes with a list of popular "threat gates".
I have never found any isolated malware that could bypass DefWall. The problem is making sure that malware will be isolated. There is a chance of:
- Someone thinking malware is okay and setting it as trusted.
- Someone getting malware from a source that isn't untrusted. Maybe by some fairly unknown email client that was installed via a CD. (Removable drives are untrusted by default, while CD/DVD drives aren't. Change this in the options menu.)
- Someone disabling DefWall's protection and forgetting to turn it on again.
Despite these chances, I believe that you are safer with DefenseWall than just an anti-virus, though they can work alongside each other.
I would recommend running a firewall too, since DefenseWall doesn't have one. (Outpost Firewall Free and Comodo Internet Security [firewall only] are both good choices.)