Ferret is a new software tool for checking host vulnerabilities. Ferret helps system administrators by quickly finding vulnerabilities that are present on a host. It is designed and implemented in a modular way: a different plug-in module is used for each vulnerability checked, and each possible output format is specified by a plug -in module. As a result, Ferret is extensible, and can easily be kept up-to-date through addition of checks for new vulnerabilities as they are discovered; the modular approach also makes it easy to provide specific configurations of Ferret tailored to specific operating systems or use environments. Ferret is a freely available open-source software implemented in Java and VBScript.