A good, short essay by net pioneer Bob Frankston exposes the misinformation and fear spread by most media accounts of the current computer virus outbreak. Building thicker walls to isolate our machines isn't an answer, Frankston reminds us, because we need to get work done.
But what does a computer firewall do? It blocks messages between machines. MSBlaster uses the "DCOM" port which is fundamental to computers working together -- if you block that port programs like Exchange can't work. The "solution" is to move all the remote calls to the same port used by the web so you can't distinguish between web activity and a remote call. All that does is up the ante so that you will have to block all web use in order to "protect" the computers.
What's worse is that in order to get any work done we must find ways to create passages through the firewall. The VPN (Virtual Private Network) allows people to "safely" connect their home computer to the corporate network. In reality it is a mechanism for defeating the firewall in order to get work done but it means that the kid (of any age) running a malicious screen saver has entrée to the entire corporate network. One can ban people from working outside the corporate offices but that doesn't help because that same screen server works fine in the office too. There is also a heavy cost in limiting the ability for people to do work.