Firewalls

Host-based firewalls are becoming all the rage. Windows XP includes a free host-based firewall, and Windows XP Service Pack 2 includes a very good, free host-based firewall, called Windows Firewall (WF). WF includes some very sophisticated management functionality that affords network administrators great control over the firewall. For instance, they can configure it to behave one way when on the internal network, another way when not. They can open up an authenticated IPsec bypass allowing all authenticated IPsec traffic to bypass the firewall, and they can set up program-based exceptions that allow certain firewall-unfriendly programs, such as instant messenger programs, to work properly. In all, the firewall has only one real or imagined shortcomingit does not perform outbound filtering. There are three reasons why: (1) Users do not understand it and therefore it will not help. As we mentioned earlier, if a dialog asking the user to make a security decision is the only thing standing between them and dancing pigs, security does not stand a chance. (2) Given that outbound filtering is a delay feature for the vast majority of users, why expend the limited available resources on that instead of giving administrators a great centrally manageable firewall? (3) Outbound filtering is available in IPsec already.

This does not, of course, mean that outbound filtering is not a worthwhile feature, just that it is not worthwhile for all users. For those who do need it, outbound filtering can be had through third-party firewalls.

We recommend using host-based firewalls on all your clients because they help stop malicious code from getting on the system in the first place.