Windows XP Firewall is much better than its Internet Connection Firewall predecessor, but it is no replacement for a 3rd-party personal firewall.
The XP firewall protects Windows XP against port scanning but there are some serious issues and limitations involved in using it.
1. The XP firewall is not a full featured firewall. Normal firewalls allow you to specifically control each TCP and UDP port but XP’s firewall does not provide you with this capability. Instead, it takes a point and click approach to enabling or disabling a few common ports.
2. The XP firewall does a good job of monitoring, examining and blocking inbound traffic but makes no attempt to filter or block outbound traffic like most 3rd-party personal firewalls. Thus, the XP firewall does not identify which programs attempt to initiate outbound network or Internet communications nor does it block the traffic when suspicious activity occurs.
This feature can be helpful in preventing many types of malware attacks that may attempt to open ports or communicate with outside servers without the user's knowledge or consent. It also means that if your system has been compromised, a hacker could use your machine as part of a distributed denial of service attack.
By default, Windows Firewall rejects all incoming traffic unless that traffic is in response to a previous outgoing request.
If you are not using the Windows firewall, you need to disable it. Running multiple software firewalls on a single computer can cause conflicts that are hard to identify and troubleshoot. Only one of the firewalls can receive the packets over the network and process them. Sometimes you may even have a conflict that causes neither firewall to protect your connection. However, you can use a hardware firewall (your router) and a software firewall (Kerio or ZoneAlarm) in conjunction.
• Using and Understanding XP's Firewall
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