If you’re running Windows XP Service Pack 2 (SP2) the new Windows Firewall is turned on by default.
Because a firewall restricts communication between your computer and the Internet, you might need to adjust settings for some programs that prefer an open connection. These adjustments are called “exceptions.”
Windows Firewall now has three settings: On, On with no exceptions, and Off.
Windows Firewall was first introduced as part of Windows XP Service Pack 2. 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. It also fixed a problem whereby the firewall policies would not be enabled on a network connection until several seconds after the connection itself was created, thereby creating a window of vulnerability. A number of additions were made to Group Policy, so that Windows system administrators could configure the Windows Firewall product on a company-wide level. XP’s Windows Firewall cannot block outbound connections; it is only capable of blocking inbound ones.
Programs may require ports to be manually opened so that the programs work correctly when Internet Connection Firewall is in use either on the local computer or on the gateway computer. You may have to manually open a port if there is a service that is running on a computer that has Internet Connection Firewall enabled that you want to make available to users on the Internet.
In computer networking, an application layer firewall is a firewall operating at the application layer of a protocol stack. Generally it is a host using various forms of proxy servers to proxy traffic instead of routing it. As it works on the application layer, it may inspect the contents of the traffic, blocking what the firewall administrator views as inappropriate content, such as certain websites, viruses, attempts to exploit known logical flaws in client software, and so forth.
An application layer firewall does not route traffic on the network layer. All traffic stops at the firewall which may initiate its own connections if the traffic satisfies the rules.
Windows Vista Firewall is a critical first line of defense to protect your computer against many types of malicious software.
A personal firewall is an application which controls network traffic to and from a computer, permitting or denying communications based on a security policy.