Internet servers -whether they offer Web services, FTP, e-mail, databases, etc.-, are normally constantly connected and can therefore receive requests from any user. As this exposure makes them prime targets for attackers and worms, system administrators should pay close attention to their security.
A basic security rule when configuring a server, is the disabling of all services that are not strictly necessary for the server to function correctly. Default settings for operating systems and applications often include additional services, which although they offer extra functions, can represent a greater risk. One such example, prone to causing problems, is the installation of communication protocols other than TCP/IP.
Similarly, while it may be necessary to have multiple ports and services open, it is not necessary that they are all indiscriminately accessible from the Internet. Once all necessary services are established, access rules should be applied either through filters in the server or by using firewalls.
System administrators should also continuously monitor access to the server to help identify potential problems. Another vital maintenance task is the prompt application of updates provided by developers, particularly security patches. In the case of SQLSlammer, a patch had long since been released which corrected the vulnerability exploited by the worm.
Finally, another good practice is to protect servers with purpose-built security solutions, such as an antivirus capable of detecting and blocking attacks at TCP/IP level, as does Panda Antivirus Appliance.