Penetration test

A penetration test is a method of evaluating the security of a computer system or network by simulating an attack from a malicious source, known as a Black Hat Hacker, or Cracker. The process involves an active analysis of the system for any potential vulnerabilities that may result from poor or improper system configuration, known and/or unknown hardware or software flaws, or operational weaknesses in process or technical countermeasures. This analysis is carried out from the position of a potential attacker, and can involve active exploitation of security vulnerabilities. Any security issues that are found will be presented to the system owner together with an assessment of their impact and often with a proposal for mitigation or a technical solution. The intent of a penetration test is to determine feasibility of an attack and the amount of business impact of a successful exploit, if discovered. It is a component of a full security audit.

Black box vs. White box
Penetration tests can be conducted in several ways. The most common difference is the amount of knowledge of the implementation details of the system being tested that are available to the testers. Black box testing assumes no prior knowledge of the infrastructure to be tested. The testers must first determine the location and extent of the systems before commencing their analysis. At the other end of the spectrum, white box testing provides the testers with complete knowledge of the infrastructure to be tested, often including network diagrams, source code, and IP addressing information. There are also several variations in between, often known as grey box tests. Penetration tests may also be described as "full disclosure", "partial disclosure" or "blind" tests based on the amount of information provided to the testing party.
The relative merits of these approaches are debated. Black box testing simulates an attack from someone who is unfamiliar with the system. White box testing simulates what might happen during an "inside job" or after a "leak" of sensitive information, where the attacker has access to source code, network layouts, and possibly even some passwords.
The services offered by penetration testing firms span a similar range, from a simple scan of an organization's IP address space for open ports and identification banners to a full audit of source code for an application.
Methodologies
The Open Source Security Testing Methodology Manual is a peer-reviewed methodology for performing security tests and metrics. The OSSTMM test cases are divided into five channels which collectively test: information and data controls, personnel security awareness levels, fraud and social engineering control levels, computer and telecommunications networks, wireless devices, mobile devices, physical security access controls, security processes, and physical locations such as buildings, perimeters, and military bases.
The OSSTMM focuses on the technical details of exactly which items need to be tested, what to do before, during, and after a security test, and how to measure the results. OSSTMM is also known for its Rules of Engagement which define for both the tester and the client how the test needs to properly run starting from denying false advertising from testers to how the client can expect to receive the report. New tests for international best practices, laws, regulations, and ethical concerns are regularly added and updated.
The National Institute of Standards and Technology (NIST) discusses penetration testing in SP800-115[1][2]. NIST's methodology is less comprehensive than the OSSTMM; however, it is more likely to be accepted by regulatory agencies. For this reason NIST refers to the OSSTMM.
The Information Systems Security Assessment Framework (ISSAF) is a peer reviewed structured framework from the Open Information Systems Security Group that categorizes information system security assessment into various domains and details specific evaluation or testing criteria for each of these domains. It aims to provide field inputs on security assessment that reflect real life scenarios. The ISSAF should primarily be used to fulfill an organization's security assessment requirements and may additionally be used as a reference for meeting other information security needs. It includes the crucial facet of security processes and, their assessment and hardening to get a complete picture of the vulnerabilities that might exist. The ISSAF however is still in its infancy.