Windows XP has come with a firewall "built-in" for some time. As of Windows XP SP2 (Service Pack 2) the provided Windows Firewall is turned on by default to protect a PC from unwanted inbound intrusions. While that is a big step forward, it is still not adequate protection when compared to other, third-party, Windows firewalls. The problem is that the Windows Firewall only provides "one-way" protection. It protects your computer from unwanted inbound access. It does not protect your PC from unwanted outbound access. So outbound threats, such as keystroke-logging Trojans or other spyware can still operate unimpeded and undetected. Your PC could also participate in denial of service attacks undetected by you or the Windows Firewall.

Another flaw of the Windows Firewall is that another application may be able to turn it off. Thus, malicious code could potentially turn off the firewall leaving an individual's PC completely unprotected.

Microsoft's Windows Vista (the next version of the Windows operating system) will improve the Windows Firewall. Windows Vista will have a two-way firewall helping to eliminate the threat of spyware and denial of service attacks from your PC. This feature fixes one of the major limitations of the Windows Firewall and makes it at least worthy of consideration as the primary firewall for your PC.

The logical next question is whether the improved firewall in Windows Vista means that there is no longer any need for a third party firewall. The honest answer at this point is that the jury is still out. Vista will not be out until later this year (2006) - most likely in the August/September timeframe, so it is difficult to understand how the firewall will perform in full use. For an individual to take advantage of Vista's improved firewall will require purchasing and installing the new operating system - something most home users may not want to do. New PCs will, of course, ship with the new operating system and the improved firewall.