Published: 2026-04-15
What Is a Penetration Test?
A comprehensive guide to penetration testing: what it is, which types exist, the methodology behind every engagement, and when your organisation needs one.
Penetration Testing Definition
A penetration test is a controlled, authorised cyberattack against an organisation's systems, networks, or applications, performed by qualified security professionals to identify vulnerabilities before malicious actors can exploit them. The goal is to simulate real-world attack techniques, measure the actual risk each finding poses to the business, and deliver a prioritised remediation roadmap that strengthens your security posture.
Unlike automated vulnerability scans that only flag potential weaknesses, a penetration test combines automated tooling with manual exploitation and creative thinking. Experienced testers chain low-severity findings into high-impact attack paths that scanners miss entirely. This human element is what separates a pen test from a checkbox exercise and turns it into a genuine measure of your organisation's resilience.
At HackersHub we conduct penetration tests following the Penetration Testing Execution Standard (PTES) and OWASP Testing Guide. Our OSCP- and OSWE-certified consultants operate from Amsterdam and have tested environments ranging from cloud-native startups to enterprise banking platforms across Europe.
Types of Penetration Testing
Every environment has a unique attack surface. Choosing the right type of penetration test ensures you focus resources where the risk is greatest.
Web Application Penetration Test
Tests your web applications for the OWASP Top 10 and business-logic flaws. Covers authentication, session management, input validation, and API endpoints exposed through the UI.
External Network Penetration Test
Simulates an internet-based attacker targeting your perimeter: public-facing servers, VPN gateways, mail servers, and cloud-hosted services visible to the outside world.
Internal Network Penetration Test
Assesses your internal network from the perspective of an insider threat or a compromised endpoint. Tests Active Directory, lateral movement paths, and segmentation controls.
API Penetration Test
Focuses on REST, GraphQL, and SOAP APIs. Tests authentication tokens, authorisation logic, rate limiting, and data-exposure risks that automated tools frequently overlook.
Mobile Application Penetration Test
Evaluates iOS and Android applications for insecure data storage, weak transport security, reverse-engineering risks, and server-side API vulnerabilities.
Cloud Penetration Test
Reviews your AWS, Azure, or GCP environment for IAM misconfigurations, over-permissive storage buckets, network exposure, and serverless function vulnerabilities.
Penetration Testing Methodology
Every HackersHub engagement follows a structured five-phase methodology aligned with the Penetration Testing Execution Standard (PTES) and the OWASP Testing Guide.
1. Scoping & Pre-Engagement
We define the scope, objectives, rules of engagement, and communication protocols. This phase ensures both parties agree on what will be tested, which techniques are permitted, and how findings will be reported.
2. Reconnaissance & Information Gathering
Our testers collect intelligence about the target environment using passive and active techniques: DNS enumeration, service fingerprinting, OSINT, and technology-stack identification.
3. Vulnerability Discovery & Analysis
Automated scanners and manual testing identify vulnerabilities. Each finding is verified to eliminate false positives and assessed for real-world exploitability in the context of your environment.
4. Exploitation & Post-Exploitation
Confirmed vulnerabilities are safely exploited to determine actual impact. Testers attempt privilege escalation, lateral movement, and data access to demonstrate what an attacker could achieve.
5. Reporting & Remediation Support
A detailed report includes an executive summary, technical findings mapped to CVSS scores, proof-of-concept evidence, and a prioritised remediation roadmap. We offer a free retest to verify your fixes.
Penetration Testing vs Vulnerability Scanning
Many organisations confuse penetration testing with vulnerability scanning. While both improve security, they serve very different purposes.
| Criterion | Vulnerability Scan | Penetration Test |
|---|---|---|
| Approach | Automated tool-driven scan | Manual testing combined with automation |
| Depth | Surface-level identification of known CVEs | Deep analysis including business-logic and chained exploits |
| False positives | High — requires manual triage | Low — every finding is verified through exploitation |
| Exploitation | No active exploitation | Safe, controlled exploitation to prove impact |
| Frequency | Weekly or monthly (continuous) | Annually or after major changes |
| Deliverable | Automated report listing CVEs | Detailed report with attack narratives and remediation guidance |
| Best for | Ongoing hygiene and patch management | Validating defences and meeting compliance requirements |
When Do You Need a Penetration Test?
Certain compliance frameworks mandate penetration testing, but regulatory requirements are only one reason to test. Below are the most common drivers.
Compliance & Certification
- SOC 2 Type II — requires evidence of regular penetration testing as part of the trust services criteria
- ISO 27001 — Annex A control A.12.6 calls for technical vulnerability management, typically satisfied by annual pentesting
- NIS2 Directive — EU-wide cybersecurity legislation requiring risk-based testing for essential and important entities
- PCI DSS v4.0 — Requirement 11.4 mandates annual external and internal penetration tests for any entity handling cardholder data
Risk-Based Triggers
- Launching a new product, platform, or customer-facing application
- Migrating workloads to a new cloud provider or hybrid architecture
- After a merger, acquisition, or significant organisational change
- Following a security incident to verify that root causes have been addressed
- Before or after a major infrastructure or code-base refactor
- When your last penetration test is more than 12 months old
Strengthen Your Security Posture
Our OSCP- and OSWE-certified penetration testers have assessed hundreds of environments across Europe — from cloud-native SaaS platforms to critical infrastructure. Get a clear picture of your risk.
Frequently Asked Questions
How long does a penetration test take?
A typical engagement runs between 1 and 4 weeks depending on scope and complexity. A single web application test may take 5–10 business days, while a combined internal and external network assessment can extend to 3–4 weeks. We provide a timeline estimate during the scoping phase.
How much does a penetration test cost?
Pricing depends on the type, scope, and complexity of the test. A focused web application assessment typically starts around €5,000, while a comprehensive multi-vector engagement can range from €15,000 to €40,000 or more. Contact us for a tailored quote based on your specific environment.
How often should you perform a penetration test?
At minimum, once per year or after any significant change to your environment — such as a major release, infrastructure migration, or acquisition. Organisations in regulated industries (finance, healthcare) often test quarterly. Continuous penetration testing programmes are increasingly common for fast-moving development teams.
What is included in a penetration test report?
A HackersHub report includes an executive summary with a risk rating, a detailed technical write-up of every finding with CVSS scores and evidence (screenshots, request/response logs), a step-by-step attack narrative showing how vulnerabilities were chained, and a prioritised remediation roadmap with quick wins highlighted.
What is the difference between black box and white box testing?
In black box testing the tester receives no internal information — simulating an external attacker with zero prior knowledge. White box (or crystal box) testing provides full access to source code, architecture diagrams, and credentials, enabling deeper coverage and more efficient use of testing time. Grey box sits in between, providing limited credentials or documentation. We recommend grey or white box for maximum value.
Will a penetration test disrupt our production systems?
No. Engagements are carefully scoped to avoid disruption. We agree on rules of engagement before testing begins, exclude fragile systems when necessary, and use safe exploitation techniques. In over a decade of engagements we have never caused unplanned downtime.
What certifications should a penetration tester hold?
Look for OSCP (Offensive Security Certified Professional), OSWE (Offensive Security Web Expert), CREST, or GPEN certifications. These require hands-on practical exams, not just theory. All HackersHub consultants hold at least one offensive-security certification.
Do you offer a free retest after remediation?
Yes. Every HackersHub penetration test includes a free verification retest within 90 days of report delivery. We retest all findings rated medium severity or higher to confirm your fixes are effective.