Metaspolit

Metasploitable is an intentionally vulnerable Linux virtual machine that can be used to conduct security training, test security tools, and practice common penetration testing techniques

Download: http://sourceforge.net/projects/metasploitable/files/Metasploitable2/

Login: msfadmin Pass: msfadmin

Rapid7 Guide: https://metasploit.help.rapid7.com/docs/metasploitable-2-exploitability-guide