Nessus Security Scanner is an open-source vulnerability scanner that you can use to audit your network. Available from http://www.nessus.org, Nessus has three primary components: a server that launches tests, a client that controls the server, and vulnerability plugins. The server/client division lets clients communicate with one server and lets you distribute tests among different users, and Nessus’s many plugins let you run different attacks against a specified host and determine which holes are exploitable.
Although originally developed for UNIX systems—in fact, the Nessus server component runs only on UNIX—Nessus’s plugins can attack Windows machines as well, and a GUI client called NessusWX is available for Windows. The scanner uses OS-fingerprinting techniques to identify the target OS and runs only plugins related to that OS.
::VulnScan & Expl0iters::
Nessus is a free, easy to use remote security scanner that is a client-server application. The application is hosted on a server (typically a Unix server), where the software can be kept up-to-date. Nessus scans any system, whether it runs Windows, Mac OS or Unix/Linux. A client server application such as nessus makes it possible to keep one easily-updatable software on a server and makes it easily accessible by as many clients as desired. Nessus also “doesn’t take anything for granted” (nessus.org). No matter how your server or workstation is set up or what operating system it uses, it will scan for security vulnerabilities. For example, say your typical webserver is serving a site on port 8080 instead of the regular port 80. Nessus will scan all open ports, regardless of common and defaulted settings. 
Product Details
This is the first of two books serving as an expanded and up-dated version of Windows Server 2003 Security Infrastructures for Windows 2003 Server R2 and SP1 & SP2. The authors choose to encompass this material within two books in order to illustrate the intricacies of the different paths used to secure MS Windows server networks.