Open-Source Security Testing Methodology Manual – This is a document of Internet security testing methodology, a set of rules and guidelines for solid penetration testing, ethical hacking, and information security analysis including the use of open source testing tools for the standardization of security testing and the improvement of automated vulnerability testing tools.
You can download it from the following link: https://packetstormsecurity.com/files/download/24576/osstmm.pdf
Source: https://packetstormsecurity.com/files/24576/osstmm.pdf.html