Introduction to Penetration Testing

Penetration testing, commonly known as pentesting, is a critical practice in cybersecurity. It involves testing a computer system, network, or web application to identify vulnerabilities that an attacker could exploit. In this blog post, we will cover the fundamentals of penetration testing, including methodologies, frameworks, and key concepts.

What is Pentesting?

Penetration testing, or pen testing for short, is like a security checkup for your computer systems. Think of it as hiring someone to play the role of a hacker to see how well your system holds up against an attack. The idea is to find and fix problems before the bad guys can find and exploit them.

Penetration testing services are regulated by legal frameworks and industry accreditation. For example, in the UK, the National Cyber Security Centre (NCSC) has the CHECK accreditation scheme.

In the UK, only CHECK-approved companies can conduct authorized penetration tests on public sector and critical national infrastructure (CNI) systems and networks.

Penetration testers often face morally questionable decisions. For instance, accessing sensitive data during a test or performing phishing attacks on employees are actions that must be pre-approved and documented in the Rules of Engagement (ROE).

The ROE outlines the scope, objectives, and legal permissions of the test.


The steps taken during a penetration test are known as the methodology. A practical methodology adapts to the specific situation. For example, testing a web application’s security requires a different approach than testing a network’s security. Here are some industry-standard methodologies:

  • Open Source Security Testing Methodology Manual (OSSTMM)1: Provides a detailed framework for testing systems, software, applications, communications, and human aspects of cybersecurity.
  • Open Web Application Security Project (OWASP)2: A community-driven framework for testing the security of web applications and services.
  • NIST Cybersecurity Framework3: Popular for improving organizational cybersecurity standards and managing cyber threat risks.

Security Models

A security model is essentially a set of rules and guidelines that help protect your computer systems. Think of it as a blueprint for building a safe, secure environment for your data and applications.

The CIA Triad

The CIA triad stands for Confidentiality, Integrity, and Availability. It is a foundational model in information security:

CIA Triad

  • Confidentiality: Ensures that sensitive information is accessed only by authorized individuals.
  • Integrity: Ensures the accuracy and completeness of data.
  • Availability: Ensures that information is accessible when needed.

Bell-La Padula Model

This model focuses on confidentiality. It uses the rules “no write down, no read up,” meaning users cannot write to lower security levels or read from higher security levels. It is commonly used in hierarchical organizations like the military and government.

Biba Model

The Biba model addresses integrity. It uses the rules “no write up, no read down,” meaning users can write to objects at or below their level but can only read from objects above their level. It is useful in environments where data integrity is paramount, such as software development.

Threat Modeling and Incident Response

Threat Modeling and Incident Response are two crucial parts of keeping your computer systems safe. They’re about planning ahead and being ready for any security issues.

Frameworks like STRIDE (Spoofing, Tampering, Repudiation, Information Disclosure, Denial of Service, Elevation of Privileges) and PASTA (Process for Attack Simulation and Threat Analysis) help in identifying and analyzing potential threats.

In the event of a security incident, a Computer Security Incident Response Team (CSIRT) is responsible for managing and mitigating the impact. The incident response process typically involves six phases:

  1. Preparation
  2. Identification
  3. Containment
  4. Eradication
  5. Recovery
  6. Lessons Learned


Penetration testing is a vital practice for identifying and mitigating security vulnerabilities. By understanding the methodologies, frameworks, and key concepts, organizations can better protect their systems and data from potential cyber threats.

By incorporating these practices and continuously improving security measures, organizations can stay ahead of potential threats and ensure robust cybersecurity.

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