See Microsoft knowledge base article 330904. If you dont use the knowledge base available on Microsoft.com then you need to be familiar with it: Most of the time you can find answers to your questions - although you may need to take some time to find the correct article. For this particular problem you can stop this type of spam by installing a firewall and/or simply turning off some of the networking options. In this instance turning off - disabling the Windows Messege Service (from the services management console) and disabling netbios over TCP/IP on your network card will solve the problem. Hoever, depending upon your network configuration you might not want to do this but merely block acccess to these ports from the internet. One of the problems with Windows systems is that some ports remain open - RPC related ports etc. If you have a windows system exposed to the internet then you must have a firewall - either hardware or software based - installed to eliminate problems with some of the ports which cannot be disabled.