This article looks at the dilemma of what to do when your software firewall is slowing down your computer to such an extent that your Internet apps such as Skype no longer work as they should. Here we discuss only firewall software that is installed on the client computer whether a Windows Notebook, Mac, Android tablet or even your mobile phone.Do I Need A Software Firewall On My Computer?Many people assume a software firewall gives them great protection whilst on the Internet but in reality it’s often more effective at protecting you on the local area network (LAN). The computers on the LAN are on the inside of the router and these machines have greater access to your machine. Almost all routers will be using NAT (network address translation) and also some form of hardware firewall. Your Internet service provider will also have firewalls in place on their networks. All of the firewalls can be defeated if you are tricked into allowing something through. Firewalls and NAT are affective at blocking all unrequested communication from the Internet, but as soon as you request something, via clicking on a web link, or agreeing to download something, you have agreed to let this through. At that point other security software may kick in like virus checkers, browser security etc, but we are not discussing those here.Although ideally you should always use a software firewall, if you are inside a NAT router and you trust the other machines on the inside of the router (inside your home), then you should be safe without using an additional software firewall.What Is NAT And Is NAT An Effective Firewall.NAT stands for network address translation and is a service that routes a single outside IP address to many internal IP addressees. Most home Internet connections use NAT. If the IP address of your computer starts with 10.x.x.x or 172.16.x.x or 192.168.x.x then you are definitely behind a NAT router.Without getting into any technical arguments, it’s fair to say that NAT provides excellent protection and therefore should be considered an effective firewall. The routers external interface is all that is actually “on the Internet”, for outside machines to reach the internal machines they have to pass through the network address translation and they cannot do that unless you set up port forwarding or the request is initiated from the inside.So What Should I Do? If you often use public Wi-Fi hotspots or other public networks you should use some form of software firewall. In this instance if you find the software is breaking the apps that you use, all you can do is try other firewall software. Usually the least effective but also the least draining on your computers resources are the default firewalls the OS vendor supplies, like “Windows Firewall”. You may find that’s your best compromise, and unless you are attending a hacker’s conference the default OS firewall should be more than sufficient.If your computer is only ever used inside your own home and you trust all the other computers that are connected to the same router then you can feel safe in relying on the NAT within the router to protect you and therefore you do not need a software firewall. We would recommend leaving the default OS provided firewall installed though as the resource usage is normally very small.Temporarily disabling your firewall or putting it in 'Game Mode' may be another option, although we found out recently that doing this with the free version of ZoneAlarm Firewall did not stop the process VSMON.exe from using masses of CPU resources. Only uninstalling it had the desired affect.Ensure your computer is up to date with all the latest security patches. The truth is that most attacks are through malware which is installed by tricking you into it; via downloading dodgy plug-ins or applications or through opening infected email attachments or using infected USB memory keys. A good virus checker is a more effective tool than any firewall to counter these threats.