Online Armor Personal Firewall Free
Note: This review addresses version 3.5 of the program, which is now in version 4.0.
Like Comodo Firewall Pro, Online Armor Free provides both a firewall and a whitelist approach to program security for Windows NT, 2000 and XP. It does not show pop-ups for many known good programs, and it scans all your installed programs when it first runs so that you can quickly tell it what to do with apps it doesn't know about.
When it does alert you about new, unknown programs, Online Armor's popups are informative but generally somewhat harder to decipher than those from Comodo. However, Online Armor goes beyond Comodo with a 'Safer Mode' that allows applications to run, but with stripped-down privileges. Safer Mode can work well for at-risk applications like Web browsers or e-mail programs, as it pulls administrator rights from such apps and prevents from making deep system changes.
Online Armor Free has a learning mode, but you'll have to manually check for program updates with the free version. A $40/year paid option adds automatic updates along with online banking protectionand other features.