Computer security is a branch of computer technology known as information security as applied to computers and networks. The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to remain accessible and productive to its intended users. The term computer system security means the collective processes and mechanisms by which sensitive and valuable information and services are protected from publication, tampering or collapse by unauthorized activities or untrustworthy individuals and unplanned events respectively. The strategies and methodologies of computer security often differ from most other computer technologies because of its somewhat elusive objective of preventing unwanted computer behavior instead of enabling wanted computer behavior.

Information assurance is related to the field of information security, in that it is primarily concerned with the protection of information systems and their contents. Generally considered the more broadly-focused of these two fields, IA consists more of the strategic risk management of information systems rather than the creation and application of security controls. In addition to defending against malicious hackers and code (e.g., viruses), IA practitioners consider corporate governance issues such as privacy, regulatory and standards compliance, auditing, business continuity, and disaster recovery as they relate to information systems. Further, while information security draws primarily from computer science, IA is an interdisciplinary field requiring expertise in accounting, fraud examination, forensic science, management science, systems engineering, security engineering, and criminology, in addition to computer science. Therefore, IA is best thought of as a superset of information security (i.e. umbrella term).

In computer security, a vulnerability is a weakness which allows an attacker to reduce a system's information assurance.

Vulnerability is the intersection of three elements: a system susceptibility or flaw, attacker access to the flaw, and attacker capability to exploit the flaw. To exploit a vulnerability, an attacker must have at least one applicable tool or technique that can connect to a system weakness. In this frame, vulnerability is also known as the attack surface.

Vulnerability management is the cyclical practice of identifying, classifying, remediating, and mitigating vulnerabilities. This practice generally refers to software vulnerabilities in computing systems.

Penetration testing is the process of evaluating the security of a computer system or network by simulating an attack from malicious outsiders (who do not have an authorized means of accessing the organization's systems) and malicious insiders (who have some level of authorized access).

Penetration tests are valuable for several reasons:

• Determining the feasibility of a particular set of attack vectors
• Identifying higher-risk vulnerabilities that result from a combination of lower-risk vulnerabilities exploited in a particular sequence
• Identifying vulnerabilities that may be difficult or impossible to detect with automated network or application vulnerability scanning software
• Assessing the magnitude of potential business and operational impacts of successful attacks
• Testing the ability of network defenders to successfully detect and respond to the attacks
• Providing evidence to support increased investments in security personnel and technology

Penetration tests are a component of a full security audit. For example, the Payment Card Industry Data Security Standard (PCI DSS), and security and auditing standard, requires both annual and ongoing penetration testing (after system changes).