A penetration test, informally pen test, is an attack on a computer system that looks for security weaknesses, potentially gaining access to the computer's features and data.
The process typically identifies the target systems and a particular goal—then reviews available information and undertakes various means to attain the goal. A penetration test target may be a white box (which provides background and system information) or black box (which provides only basic or no information except the company name). A penetration test can help determine whether a system is vulnerable to attack, if the defenses were sufficient, and which defenses (if any) the test defeated.
Security issues that the penetration test uncovers should be reported to the system owner. Penetration test reports may also assess potential impacts to the organization and suggest countermeasures to reduce risk.
The goals of a penetration test varies depending on the type of approved activity for any given engagement with the primary goal focused on finding vulnerabilities that could be exploited by a nefarious actor, and informing the client of those vulnerabilities along with recommended mitigation strategies.
Penetration tests are a component of a full security audit. For example, the Payment Card Industry Data Security Standard requires penetration testing on a regular schedule, and after system changes.