A firewall is designed to block unauthorized access while permitting authorized communications. It is a software which is configured to permit or deny computer applications based upon a set of rules and other criteria.
Comodo free personal firewall is one of the best and popular free firewall software in the market.It also offer free internet security suite (free antivirus + free firewall).Its installation is easy.Comodo firewall send alerts and updates automatically.And it has the most iportant feature called Default Deny Protection.
ZoneAlarm was one of the best free firewalls available for Windows. It has Inbound Firewall,Outbound Firewall, Automatic Stealth Mode, Anti-phishing, Site Check,Identity Protection Services, DefenseNet,Online Backup (2GB Free), Detects & blocks behavior of unknown viruses, Detects hacker programs impersonating good programs, Stops hacking disguised as harmless network transmissions,Blocks unknown malware from transmitting to hackers,Makes you invisible to hackers by defaults,Uses threat data from users worldwide to detect attacks, Automated, fewer alerts than other firewalls, simple setup,automatic updates.
PC Tools Firewall Plus is a powerful free personal firewall for Windows. Pc tools firewall features: Network Awareness, Data Leakage Protection, Windows Filtering Platform Support, Easy to configure with normal and expert user modes, Optional password protection for rules and settings. No interruptions when playing full-screen games, Automatic application blocking , network shielding, Experienced users can create or edit advanced packet filtering rules, IPv6 support.
Online Armor Free has Kernel Mode Security,Execution Protection,Termination Protection,Limited Autostart Protection, Standard Mode Firewall,Keylogger Detection,Tamper Protection, Script/Worm protection,Program Guard. It doesn’t have automatic updates and a built-in help.
Outpost Firewall Free is also good firewall program for average users. It has a simplify alert message system and it is easy to adjust HIPS monitoring.Some of it’s features are Firewall (network protection),Proactive host protection,Self protection. There is no automatic update.