From Sygate Technologies:
Free for personal use, Sygate Personal Firewall provides best-of-breed security in a user-friendly interface, protecting your PC from hackers, Trojan horses, and DOS attacks. New features include deep-packet inspection, anti-application-hijacking, a log dampener, and enhanced logging. Sygate Personal Firewall is the first free PC firewall to offer protection from malicious code intrusions, keeping the information on your PC safe and private. For multiple-seat licenses for businesses or advanced users, our award-winning Sygate Personal Firewall Pro is available starting at $39.95.