What happens during a penetration test is a structured, time boxed simulation of real world attacks against your systems to find and verify exploitable security weaknesses. A qualified tester attempts to break in using agreed rules, then documents exactly how it happened and how to fix it. The result is a prioritized, evidence backed roadmap to reduce risk quickly.
Why penetration tests exist and what they are not
Penetration testing, often called pen testing, is designed to validate whether vulnerabilities can be exploited in your environment, not just whether a scanner can detect them. It differs from a vulnerability assessment because it includes manual investigation, chaining of weaknesses, and proof of impact. It is also not the same as red teaming, which is typically longer, stealthier, and focused on measuring detection and response rather than producing a comprehensive list of findings.
In many regions and industries, penetration tests support compliance and due diligence. For example, organizations in the United States working with payment card data often use pen tests to support PCI DSS requirements, while organizations in the United Kingdom and across the EU commonly use pen tests as part of ISO 27001 controls, NIS2 readiness, and broader risk management. Regardless of geography, the core phases are consistent.
Phase 1: Scoping, goals, and rules of engagement
The first part of what happens during a penetration test is defining exactly what will be tested, why, and under what constraints. This phase prevents surprises, reduces business disruption, and ensures the test produces actionable outcomes rather than noise.
Defining scope and test type
Scope includes assets (domains, IP ranges, applications, APIs, cloud accounts, mobile apps), environments (production vs staging), and exclusions (for example, life safety systems, certain third party services, or fragile legacy applications). The team also agrees on the test type:
- Black box: minimal information, simulating an external attacker.
- Gray box: limited credentials or architecture context, simulating a user or partner.
- White box: full access to documentation and code or configs, maximizing coverage.
Rules, communications, and safety controls
Rules of engagement define allowed techniques, testing windows, points of contact, and escalation paths if a critical vulnerability is discovered. Practical safeguards often include rate limits, agreed denial of service exclusions, dedicated test accounts, and approved IP addresses so security teams can distinguish test traffic from hostile activity. Legal authorization is essential, especially for organizations operating across jurisdictions such as the US and Canada, or the UK and EU, where contractual and privacy obligations vary.
Phase 2: Information gathering and reconnaissance
The next stage of what happens during a penetration test is building an accurate picture of your attack surface. Reconnaissance combines open source intelligence with technical discovery to identify what is exposed and how it is configured.
External recon and attack surface mapping
Testers enumerate domains and subdomains, identify hosting and cloud providers, and map exposed services. They may review certificate transparency logs, public code repositories, leaked credential sources, and third party references that reveal hidden endpoints. For global organizations with offices in places like New York, London, Singapore, or Sydney, recon often highlights regional infrastructure differences, such as separate tenant setups, localized SaaS integrations, or country specific web properties.
Internal discovery (when in scope)
For internal tests, the team assesses the internal network from a defined foothold, such as a VPN connection or an onsite drop box device, depending on the agreed model. They identify network segments, directory services, exposed management interfaces, and high value targets like identity providers, CI/CD systems, and backup servers.
Phase 3: Vulnerability analysis and test planning
After reconnaissance, testers analyze identified services and applications to pinpoint weaknesses worth validating. Automated scanning tools may be used, but the distinguishing element is manual verification and context. A potential issue becomes a finding only after the tester confirms it is real, exploitable, and relevant to your environment.
At this point, testers prioritize attack paths that reflect realistic threats. For example, an internet exposed admin portal in a cloud environment may be higher risk than an obscure service on a restricted subnet. The team also considers your business context, such as customer data, regulated workloads, and critical operational systems.
Phase 4: Exploitation and gaining access
This is the phase most people think of when asking what happens during a penetration test. Testers attempt to exploit validated weaknesses to demonstrate impact in a controlled way, following the agreed safety rules.
Common exploitation approaches
- Web application attacks: authentication bypass, injection flaws, insecure direct object references, server side request forgery, and misconfigured access controls.
- API testing: broken authorization, mass assignment, improper input validation, weak token handling, and excessive data exposure.
- Cloud misconfiguration validation: overly permissive IAM roles, exposed storage buckets, insecure security groups, and overly broad service principals.
- Network and system exploits: weak protocols, unpatched services, insecure remote access, and credential reuse.
Responsible testers avoid unnecessary data access. They often prove access by retrieving a limited sample, creating a harmless marker file, or demonstrating the ability to assume a role, rather than extracting sensitive datasets.
Credential testing and authentication checks
When authorized, testers assess password policy strength, multi factor authentication coverage, session management, and account lockout behavior. They may test for common credential issues such as default credentials, shared admin accounts, and password spraying resistance. If your organization uses single sign on across regions, such as Azure AD or Okta for teams in California and the UK, the tester will often examine how identity controls are enforced consistently across applications.
Phase 5: Privilege escalation and lateral movement
Once an initial foothold is established, what happens during a penetration test often includes escalating privileges and moving laterally to reach higher value assets. This models how attackers turn a small weakness into a major breach.
Examples include escalating from a low privilege user to an administrator role due to misconfigured permissions, exploiting token leakage in a CI pipeline, or accessing internal services through a compromised host. In internal environments, testers may assess Active Directory weaknesses, delegation settings, and overly permissive group memberships. In cloud environments, they may chain IAM permissions to obtain broader access.
Phase 6: Post exploitation validation and impact demonstration
Impact is validated carefully. The objective is to demonstrate risk in business terms: data exposure, account takeover, unauthorized transactions, service disruption potential, or compliance impact. For a retailer, the story might be access to customer records; for a healthcare provider, it might involve protected health information; for a SaaS company, it might be cross tenant data access.
Testers document evidence such as request and response samples, screenshots, logs, and exact steps to reproduce. They also track which controls failed: missing input validation, incorrect authorization checks, weak segmentation, or inadequate monitoring.
Phase 7: Cleanup and restoring conditions
Professional testing includes cleanup. Temporary accounts, test payloads, and created artifacts are removed. Any configuration changes made for testing are reverted unless explicitly agreed otherwise. This is particularly important in production environments and regulated settings, including organizations operating in the US financial sector or UK public services, where audit trails and change management processes matter.
Phase 8: Reporting, prioritization, and remediation guidance
The report is often the most valuable deliverable in what happens during a penetration test. It translates technical findings into prioritized actions your teams can execute.
What a strong report includes
- Executive summary: overall risk, key themes, and business impact.
- Scope and methodology: what was tested, dates, assumptions, and limitations.
- Findings list: severity, likelihood, impact, affected assets, and evidence.
- Reproduction steps: clear steps and proof to validate fixes.
- Remediation advice: specific, realistic recommendations and compensating controls.
Many organizations align severity ratings with common frameworks and internal risk models. The best reports also note positive security controls observed, such as strong MFA enforcement or effective segmentation, so teams know what to preserve.
Phase 9: Debrief, retesting, and continuous improvement
A debrief session ensures stakeholders understand the findings and how to address them. Engineering teams can ask questions, clarify reproduction details, and agree on remediation priorities. After fixes are deployed, retesting confirms vulnerabilities are resolved and no new issues were introduced.
Over time, organizations mature by integrating lessons into secure development practices, infrastructure as code guardrails, logging and monitoring improvements, and regular security testing. For distributed teams across multiple time zones, aligning retest windows and change freezes is part of making the process repeatable.
How to prepare so your test delivers maximum value
To get the most from the engagement, provide an accurate asset inventory, nominate a responsive technical contact, and ensure test accounts represent real roles. If possible, align the test with a release cycle so findings can be addressed quickly. For cloud and SaaS heavy environments, confirm logging is enabled so you can learn from detection signals during the exercise, even if the test is not a full red team.
Conclusion
Understanding what happens during a penetration test helps you treat it as a practical security improvement project, not a one time checkbox. When scoping is clear, testing is controlled, and reporting is actionable, a pen test can quickly uncover exploitable paths and guide effective remediation across applications, networks, and cloud services. If you plan the engagement well and follow through with fixes and retesting, you will measurably reduce risk and strengthen confidence with customers, partners, and regulators.
Frequently Asked Questions
How long does a penetration test usually take?
How long does a penetration test usually take?
What happens during a penetration test depends on scope and depth, but many small web app tests take 3 to 7 business days of testing plus reporting time. Larger environments with internal networks, cloud services, and multiple apps can take several weeks. Retesting typically adds 1 to 3 days after fixes are deployed.
Will a penetration test disrupt production systems?
Will a penetration test disrupt production systems?
What happens during a penetration test is designed to avoid disruption through rules of engagement, rate limiting, and explicit exclusions for denial of service techniques. However, any active testing carries some risk, especially with legacy systems. Reduce impact by using staging where possible, scheduling maintenance windows, and ensuring rapid communication channels during testing.
What is the difference between a vulnerability scan and a penetration test?
What is the difference between a vulnerability scan and a penetration test?
What happens during a penetration test includes manual validation and controlled exploitation to prove real impact, while a vulnerability scan primarily identifies potential issues using automated checks. Scans are useful for coverage and frequency, but they can produce false positives and lack context. Pen tests prioritize exploitable paths and provide detailed reproduction and remediation guidance.
What should we provide to the testers before the engagement begins?
What should we provide to the testers before the engagement begins?
What happens during a penetration test goes smoother when you provide an accurate scope list, test accounts for key roles, architecture notes for complex systems, and emergency contacts. Also share any hard constraints, such as change freezes or third party restrictions. For internal tests, confirm VPN access or onsite procedures and logging visibility for your security team.
How often should a company run penetration tests?
How often should a company run penetration tests?
What happens during a penetration test is most valuable when timed to meaningful change. Many organizations test annually at minimum, plus after major releases, infrastructure migrations, or new authentication deployments. If you operate high risk services or handle regulated data, consider more frequent targeted tests and retesting after significant remediation to confirm fixes.
