Classifications of hackers

White hat
A white hat hacker breaks security for non-malicious reasons, perhaps to test their own security system or while working for a security company which makes security software. The term "white hat" in Internet slang refers to an ethical hacker. This classification also includes individuals who perform penetration tests and vulnerability assessments within a contractual agreement.

Black hat
A "black hat" hacker is a hacker who "violates computer security for little reason beyond maliciousness or for personal gain" .Black hat hackers break into secure networks to destroy data or make the network unusable for those who are authorized to use the network.

Grey hat

A grey hat hacker is a combination of a Black Hat and a White Hat Hacker. A Grey Hat Hacker may surf the internet and hack into a computer system for the sole purpose of notifying the administrator that their system has been hacked. 

Penetration testing methodology

Information gathering

Network mapping

Vulnerability identification

Penetration

Gaining access and escalation

Enumerating further

Compromising remote user/sites

Maintaining Access

Covering tracks

Penetration testing

A penetration test is a method of evaluating the computer security of a computer system or network by simulating an attack from external threats and internal threats. The process involves an active analysis of the system for any potential vulnerabilities that could result from poor or improper system configuration, both known and 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.Security issues uncovered through the penetration test are presented to the system's owner.Effective penetration tests will couple this information with an accurate assessment of the potential impacts to the organization and outline a range of technical and procedural countermeasures to reduce risks.