*Updated 12/10/2026

The five stages of penetration testing covered in this guide are reconnaissance, scanning, vulnerability assessment, exploitation and reporting. Together, they help organisations identify security weaknesses, understand how attackers could exploit them and prioritise remediation.

Penetration testing, also known as pen testing, is an authorised security assessment that combines specialist expertise with automated tools to investigate vulnerabilities and demonstrate their potential impact.

In 2026, your testing scope needs to reflect how your business operates. That could include internal networks, internet-facing applications, cloud environments, APIs and identity systems. The aim is to answer a practical question: where could an attacker gain access, and what could they do next?

Before testing begins: Agree the scope

Although this article groups the technical process into five stages, methodologies use different phase names and structures. Planning and authorisation must come before testing.

Your organisation and testing provider should agree which systems are in scope, the objectives, permitted techniques, testing windows and any exclusions. They should also establish emergency contacts, data-handling requirements and conditions for pausing the test.

These rules of engagement give testers clear boundaries and help manage operational risk. NIST identifies them as guidelines and constraints established before a security test begins.

1. Reconnaissance: Understand the target environment

Reconnaissance is the information-gathering stage of penetration testing. It helps testers understand the environment and identify potential entry points within the agreed scope.

This may involve reviewing domain names, IP addresses, publicly accessible services, application information and details supplied by your technical teams.

The information available depends on the engagement. Some tests begin with limited knowledge of the environment, while others include architecture documentation, test accounts and access to relevant configurations.

The outcome is a clearer picture of the systems being assessed and where further investigation is needed.

2. Scanning: Identify exposed services and potential weaknesses

Scanning uses technical tools to discover active systems, open ports, services and potential vulnerabilities.

It can help identify outdated software, exposed administrative interfaces and configuration issues. For applications, discovery may also involve mapping accessible pages, endpoints and functionality.

However, a scanner finding is not automatically a confirmed security risk. Results need to be reviewed in context: is the affected service accessible, are mitigating controls present, and does the finding apply to the actual configuration?

Scanning gives testers a starting point for deeper investigation.

3. Vulnerability Assessment: Analyse and validate findings

During vulnerability assessment, testers examine potential weaknesses to establish which are relevant and how they could affect the organisation.

This combines automated results with manual analysis. For web applications, testing may cover authentication, authorisation, session management, input validation and business logic. These are among the areas addressed by the OWASP Web Security Testing Guide.

Manual investigation is particularly important where a weakness depends on how an application works. For example, a user might be able to access another customer’s information despite having a valid account and successfully authenticating.

Testers also consider how weaknesses interact. An exposed service and excessive account permissions may create a more serious risk together than either finding suggests in isolation.

This stage helps determine which issues warrant controlled exploitation and further impact assessment.

4. Exploitation: Demonstrate the potential impact

Exploitation involves controlled attempts to use identified weaknesses within the agreed rules of engagement.

The purpose is to establish whether a vulnerability can be exploited and what access it could provide. Depending on the scope, testers may assess whether they can bypass access controls, gain additional privileges or reach other systems.

For example, a test could demonstrate that a low-privileged account can access restricted functionality. That gives the organisation evidence of the weakness and its consequences.

The objective is to demonstrate impact using the minimum necessary activity. Causing disruption or extracting large volumes of sensitive data is not a routine requirement. Any potentially disruptive techniques need specific consideration and agreement before use.

Testers should record evidence and communicate significant findings promptly so the organisation can take action.

5. Reporting: Turn findings into remediation

The penetration testing report explains what was tested, what was discovered and what the organisation should do next.

A useful report should include:

• An executive summary explaining the business implications.
• The scope, approach and limitations of the assessment.
• Findings supported by evidence and risk ratings.
• Clear remediation recommendations.

Technical teams need enough detail to understand and address each issue. Business stakeholders need to understand the potential consequences and which improvements deserve priority. The NCSC’s guidance similarly emphasises reporting security issues, their risk and methods of resolution.

Reporting should lead to action. Assign owners, agree remediation deadlines and arrange retesting to check whether fixes address the original findings.

What should penetration testing cover in 2026?

Start with the systems, data and services your organisation depends on. A testing programme should reflect changes to that environment, including new applications, cloud deployments, integrations and access arrangements.

Ask whether the scope covers the connections between systems as well as individual components. An application may appear secure while weaknesses in its API or permissions expose sensitive information.

Where AI-enabled applications are involved, discuss their specific functionality and risks during scoping. Do not assume a conventional infrastructure or application test automatically assesses every AI-related behaviour.

Testing also needs to sit alongside ongoing vulnerability management. A penetration test provides evidence about the agreed scope at a particular time; subsequent changes can introduce new weaknesses.

Why choose Integrity360 for Penetration Testing?

Integrity360’s CREST-accredited penetration testing services assess networks, applications, cloud environments, identities and connected devices. Our specialists combine automated tools with manual testing to investigate attack paths and explain their potential business impact.

We tailor engagements to your environment, objectives and risk profile, providing clear findings and practical remediation guidance to help your teams prioritise improvements.

Explore Integrity360’s penetration testing services and speak to our team about your testing requirements.

FAQs

What Is Penetration Testing?

Penetration testing is an authorised assessment in which security specialists identify weaknesses and attempt controlled exploitation. It helps organisations understand how vulnerabilities could be used and what impact a successful attack might have.

What Are the Five Stages of Penetration Testing?

This guide describes five stages: reconnaissance, scanning, vulnerability assessment, exploitation and reporting. Different methodologies group these activities differently. Scoping and authorisation come before testing, while remediation and retesting follow the findings.

What Is the Difference Between Vulnerability Scanning and Penetration Testing?

Vulnerability scanning uses automated tools to identify potential weaknesses, particularly known vulnerabilities. Penetration testing adds specialist investigation and controlled exploitation to assess whether weaknesses can be used and what the consequences could be.

How Often Should Penetration Testing Be Carried Out?

Testing frequency should reflect your organisation’s risk, the importance of the systems involved and applicable contractual or compliance requirements. Significant changes to applications, infrastructure or access arrangements should also prompt a review of testing needs.

Can Penetration Testing Disrupt Business Operations?

Testing can carry operational risk, particularly when production systems are involved. Clear scope, agreed techniques, suitable testing windows and communication help manage that risk. A responsible provider should explain potential impacts rather than promise that disruption is impossible.

What Happens After a Penetration Test?

Your teams should review the findings, prioritise remediation and assign responsibility for fixes. Retesting then checks whether those changes have resolved the identified weaknesses. Findings can also inform improvements to development, configuration and vulnerability management processes.

Does Penetration Testing Guarantee That an Organisation Is Secure?

No. A penetration test assesses a defined scope within an agreed timeframe. It cannot identify every possible weakness or guarantee protection against future attacks. It should form part of an ongoing security programme.