You don’t need a windows firewall if you have a Firewall installed on your router. With the new Windows XP Service Pack 2 Security Alert system, do we still need a firewall to stop outgoing traffic? If we have a router (Linksys), that will take care of everything, which means we have to disable Windows Firewall to avoid false alarms?
There are many misunderstandings about firewalls, routers, and security software. When Windows XP Service Pack was released two definitely put security, and in particular the firewall, “in your face.” Later versions of Windows now also include the firewall and turn it back on by default. It’s a great opportunity to find out what you need…and what you don’t.
A firewall filters network traffic. A firewall protects against certain kinds of network ingress problems. If you’re not behind a router or other firewall, you’ll need to turn on Windows Firewall.
Each computer must be behind a firewall of some sort. In general, hardware firewalls, usually provided by NAT routers, keep malicious network traffic from ever reaching your computer, while software firewalls, such as Windows Firewall, drop malicious traffic after it has passed. has actually reached your computer. But it doesn’t take that much. If you have a router with Network Address Translation, or NAT, enabled (most consumer grade routers do this by default) then there is no need to turn on Windows Firewall. In fact, you can tell the new Windows Security Center that you manage your own firewall. If you’re not behind a router or other firewall, you’ll at least want to turn on the Windows firewall.
Now, one word from the original question is worth a comment: “exit”. Consumer-grade routers will keep you safe from threats that are incoming from your network, but they won’t filter or alert you to any malware that’s already on your computer trying to plug out. Windows Firewall has a limited number of outbound traffic alerts, and other software firewalls that you can install separately to use in place of Windows Firewall can be configured with a wide range of outbound protection. There are a wide variety of opinions on this, but personally, I’m pretty happy just behind a router and unmonitored for outgoing threats. But regardless, you need a firewall, whether it’s an external router, a software package that you install, or, at a minimum.