Free Personal Firewall Software

Filseclab Personal Firewall Professional Edition

This Windows firewall filters inbound and outbound traffic. You can configure which applications on your system is allowed to access the Internet, although by default, it automatically allows certain applications (such as those from the company itself, or those signed by Microsoft) outbound access without question.

Comodo Personal Firewall

Comodo Personal Firewall is a Windows 2000/XP firewall, that filters both inbound as well as outbound traffic. Among its features are the ability to detect application hijacking attempts via its application and component behaviour monitor, self protection against termination attempts by malware, protection of your PC during startup, etc. Note: they require you to activate the firewall and supply your email address.

GhostWall

GhostWall is a packet filtering firewall with low resource usage and latency. It works on both 32 bit and 64 bit Windows.

Guarddog

Guarddog is a firewall configuration utility for Linux iptables. It also lets you maintain and modify the firewall in place. It uses a "what is not explicitly allowed, is denied" philosophy. The software is released under the GNU GPL.

SoftPerfect Personal Firewall

SoftPerfect Personal Firewall is a rule-based Windows network firewall that filters IP and non-IP traffic, supports configurations for multiple network adaptors, has a learning mode and comes with a set of predefined rules.

Jetico Personal Firewall

Jetico Personal Firewall is a Windows 98/ME/NT/2000/XP firewall that has network packet filters, network events filters (that allows you to block application level events) and process activity filters (that hopefully blocks application hijacking attempts where a trojan uses your browser to send information to the internet).

Firestarter - Free Linux Firewall Tool

Firestarter is an easy-to-use free firewall tool for Linux that has a wizard that allows you to customize your firewall, a real-time firewall monitor that allows you to view intrusion attempts, a graphical interface that works under GNOME and KDE, and support for Linux kernels 2.4 and 2.6. For those who aren't brave enough to muck around with netfilter / iptables, Firestarter is one way to set up your system so that it is protected from intrusions.

Sunbelt Kerio Personal Firewall

Kerio Personal Firewall is free for home use. It controls traffic from your computer to the Internet (thus useful for blocking spyware, adware, and other software that call home to the Internet behind your back) as well as traffic from the Internet to your computer. This is a Windows firewall.

ZoneAlarm

ZoneAlarm is an easy to use and free personal firewall that is used by many people on the Internet. The free versions allows you to decide which applications you can allow to access the Internet, but does not allow you to block specific IP addresses. This is a Windows firewall. If you want comprehensive protection for your computer, you might want to consider their commercial offering, ZoneAlarm(R) Internet Security Suite 6 which includes a firewall as well as antivirus, antispyware, antitrojan , identity theft protection, phishing and spam blocker, etc.

Sygate Personal Firewall

This firewall allows you to set policies regarding applications that may be allowed to access the Internet, trusted IP addresses, ports, protocols, etc. This is a Windows firewall. Warning: this firewall is no longer maintained. The link above points to a third party download site (Simtel) that loads pop-up windows.