Nessus

Nessus is a multiplatform tool to let network administrators check for security gaps on a local network or personal computer, regardless of the operating system installed on the machines. It does this by trying to detect the presence of a series of known vulnerabilities which make up part of its extensive plugins database. Users can define their own security policies according to their needs, eliminating areas that don't affect the particular network they work with. For example, you can get rid of the analysis for Unix vulnerabilities if you have a Microsoft Windows network. The plugins tab under the option to edit or create a policy lists all the resources that Nessus can process and that belong to different operating systems, network protocols, firewalls, SGBD, etc.