The Metasploit Project is an open source project that provides a public resource for researching security vulnerabilities and developing code that allows a network administrator to break into his own network to identify security risks and document which vulnerabilities need to be addressed first.
The Metasploit Project offers penetration (pen) testing software and provides tools for automating the comparison of a program's vulnerability and its repaired (patched) version. Anti-forensic and advanced evasion tools are also offered, some of them built into the Metasploit Framework.
Metasploit Framework, the Metasploit Project's best-known creation, is a software platform for developing, testing, and executing exploits. It can be used to create security testing tools and exploit modules and also as a penetration testing system. It was originally created as a portable network tool in 2003 by HD Moore.
The Metasploit Project also offers Metasploit Express, Metasploit Pro, the Opcode Database (currently out of date) and a shellcode database. Shellcode is a type of exploit code in which bytecode is inserted to accomplish a particular objective. Common shellcode objectives include adding a rootkit or performing a reverse telnet back to the attacker's machine. Metasploit also offers a payload database, allowing the pen tester to mix and match exploit code and objectives.
In 2009, the Metasploit Project was acquired by computer security company Rapid7. Metasploit Express and Metasploit Pro are "open core" versions of the Metasploit Framework, with more features added. (Open core is an approach to delivering products that combine open source and proprietary software.) Rapid7 continues to develop Metasploit in collaboration with the open source commmunity.