Microsoft released his own firewall with his new release of windows XP service pack 2. Previously it is known as ICF (Internet Connection Firewall).Then Microsoft integrated all his later version of operating system with his firewall. With windows 2003 server firewall was released with service pack 1.Every type of network connection, whether it is wired, wireless, VPN, or even FireWire, has the firewall enabled by default, with some built-in exceptions to allow connections from machines on the local network. This provides security defense against unauthorized access between your computer and Internet.
By default windows firewall is enabled for security purpose. However we can disable firewall. To control windows firewall Goto Start –> Control Panel –> Select Windows Firewall. Form their we can manage and control firewall.
How Windows Firewall works?
When unauthorized access from internet tries to connect your computer and request some information, windows firewall gets activated and blocks the connection. In case if you are running a program like google talk it gives a alert message to release/unblock that particular application. If released the application get access or if blocked the application gets restricted for use.
Windows firewall helps to avoid computer virus and worm. However it will not detect or clean any virus or worms. It also blocks email with dangerous attachments and also block spam and unsolicited e-mail.