Firewalls are software which prevents illegal access to your computer. It acts like a watchman who allows only certain people to access your grounds.
Some security packages already provide these firewalls as part of their product. Windows® XP and above provide firewalls in-buit in the Operating System (OS).
NetVeda Safety.Net Firewall
This is another good firewall with inbuilt application control and content filtering. This software has inbound and outbound filtering. It is a good firewall which runs on the Windows Platform like Windows 95/98/Me/2000/XP. There is no multilingual capabilities in this software and you need to register to be able to download it (Requires you Email Address).
Filseclab Personal Firewall Pro
This software besides being your firewall can provide you with basic protection from spyware. Top-notch firewall for the Windows environment. Does in-bound and out-bound traffic monitoring and has many other features.
Firestarter - Free Firewall
This is a free firewall for Linux users which has a graphical user interface (GUI), filters inbound and outbound traffic, allows you to maintain a blacklist of what to filer and what not to filter. This software is open-source.
GhostWall - Free Firewall
Low-consumption software which monitors your network traffic. When attacks occur, it notifies you and show you from which country the attack is occurring.
Guarddog - Free Firewall
Firewall for Linux geeks.
Kerio (Now Sunbelt) Limited free edition - Free Firewall
This is a firewall for Windows® users. This version is free but there is also a paid commercial version. Update: Kerio Firewall has now been rebranded and is being released under the name of Sunbelt-Kerio Personal Firewall. You can download it here:
Supported Platforms are: Windows 2000/XP/2003 and in near future, Vista. It is also availble in multiple languages.
Omniquad Personal Firewall Freeware
Again another personal firewall by, well, Omniquad. Works on Windows®.
Online Armor Free Edition - Free Firewall
Free firewall software for Windows NT, 2000, XP. No multi-lingual support availble for this software.
Outpost Firewall FREE
Free stripped down version of the full-fledged version, the latter which has more features than this one.
Besides the antivirus software, there is also Comodo Firewall which runs only on Windows® 2000 and XP SP2, and Vista. It also supports multiple languages.
PC Tools Firewall Plus
Good firewall for Windows. Provides adequate protection, but you need to register by providing an email address to get an activation code.
Premedius Firewall Lite
Yet another Windows® firewall which is for personal use only.
Jetico Personal Firewall
A 32-bit firewall which runs on all Winodws systems except Windows 95. The freeware version has been abandoned and there is no support. However, it is very functional and has multilingual capabilities and supports 64-bit platforms.
Free firewall, yet again for Windows® which has many cool features.
SensiveGuard - Free Firewall
Runs only on Windows® 2000 and XP SP2.
SoftPerfect Firewall (Personal Edition)
Yet another freefirewall.
Sygate Personal Firewall
Yet another free firewall.
x-Wall Series - Free Firewall
The whole of the package is paid, but the firewall is free.
AppArmor - Free Firewall
A security suite for Linux, which is open source and free. Stops hacking and exploitation of the softwares on the server.
WIPFW - Free Firewall
Based on FreeBSD's IPFW, this one is a Windows firewall.
Zone Alarm Firewall
One of the best firewall software is actually free! Grab it!