Please remember that VulnHub is a free community resource so we are unable to check the machines that are provided to us. Before you download, please read our FAQs sections dealing with the dangers of running unknown VMs and our suggestions for "protecting yourself and your network. If you understand the risks, please download!
Some folks may already be aware of Metasploitable, an intentionally vulnerable virtual machine designed for training, exploit testing, and general target practice. Unlike other vulnerable virtual machines, Metasploitable focuses on vulnerabilities at the operating system and network services layer instead of custom, vulnerable applications. I am happy to announce the release of Metasploitable 2, an even better punching bag for security tools like Metasploit, and a great way to practice exploiting vulnerabilities that you might find in a production environment.
For download links and a walkthrough of some of the vulnerabilities (and how to exploit them), please take a look at the Metasploitable 2 Exploitability Guide.