What are penetration tests and how to secure IT infrastructure?

In today’s cyber threat landscape, having security features such as a firewall or antivirus is an absolute must. But how can you be sure that these protections are effective and properly configured? Can they fend off an attack by a determined, creative hacker? The answers to these questions cannot be found in the advertising brochures of software manufacturers. They must be verified in practice, under controlled combat conditions.

That’s what penetration testing, often called pentesting, is for. It’s an authorized, ethical simulation of a real cyber attack, conducted by certified security professionals. The goal of a pentest is not to cause damage, but to think and act like a real hacker to find and exploit security vulnerabilities before criminals do. In this guide, we’ll explain what penetration testing is, how it’s done, and why it’s one of the most important parts of building real resilience in any modern organization.

What are penetration tests and how do they simulate the actions of a real hacker?

Penetration testing (penetration tests, pentests) is an advanced and proactive method of assessing the security of IT systems, which involves launching a controlled attack on a client’s infrastructure, network or applications. The main goal is to practically verify the effectiveness of existing security features by attempting to bypass or break them. The pentester, or ethical hacker, does not rely on theory alone, but actively seeks and attempts to exploit vulnerabilities found.

Simulating the actions of a real hacker involves using the same techniques, tactics and procedures (TTPs) used by cybercriminals. Pentesters use identical tools to scan networks, search for software vulnerabilities, attempt to crack passwords or launch attacks on web applications. They think creatively, trying to combine seemingly harmless single vulnerabilities into complex attack chains that can lead to full system compromise.

Unlike a real attack, penetration tests are fully controlled and authorized. Before testing begins, a pentesting company (such as nFlo) signs a detailed contract with the client that precisely defines the scope of the test (which systems and IP addresses can be attacked), the timeframe and the rules of conduct. All activities are monitored, and the goal is not to steal data or sabotage, but to document the vulnerabilities found and make specific recommendations to fix them.

What are the key differences between black box, white box and grey box tests?

Penetration tests can be conducted according to different scenarios, which differ in the level of knowledge the pentesting team has about the system under test before launching the attack. There are three main approaches: black box, white box and grey box.

Black box (black box) testing: In this scenario, the pentesting team has virtually no knowledge of the internal construction and configuration of the infrastructure under attack. It only receives basic information, such as the company’s name or website address – exactly like a real hacker launching a reconnaissance from the outside. The goal is to see what the attacker is able to discover and achieve, starting from scratch. These tests perfectly simulate an attack by an outside criminal unfamiliar with the company.

White box testing: This approach is at the opposite extreme. The pentesting team is given full and detailed knowledge of the environment under test. This can include access to application source code, network architecture diagrams, technical documentation and even administrative accounts. The goal is an in-depth and comprehensive security analysis, allowing detection of even very subtle and deeply hidden vulnerabilities that would be impossible or very time-consuming to discover in a black box test. These tests simulate a threat from an advanced attacker who already has knowledge of the system, or an insider threat.

Grey box testing: This is the most common and sustainable approach, a compromise between the two above. Pentesters have limited, partial knowledge of the system, similar to what a regular authenticated user would have. They are usually given a standard account of the application under test or basic information about the architecture. This allows them to effectively test security “from the inside” and see if a regular user is able to, for example, escalate their privileges and access data they shouldn’t.

Why are regular pentests necessary to verify the effectiveness of security features?

Implementing even the most expensive and advanced security systems offers no guarantee if their effectiveness is not regularly verified in practice. The IT environment is dynamic, and the threat landscape changes every day. Regular penetration testing is an essential component of a mature cyber security strategy, as it allows an objective assessment of an organization’s real resilience.

First, pentests verify that existing security is properly configured and integrated. It often happens that a company invests in a new-generation firewall, but due to misconfiguration it leaves dangerous ports open. A penetration test will quickly detect such an oversight. It verifies the overall state of the defense, not just individual components, checking that they interact effectively.

Second, the IT environment is constantly changing. New applications are deployed, new servers are added, configurations are changed. Each such change can inadvertently introduce a new security vulnerability. Regular, recurring pentests (e.g., once a year or after every major infrastructure change) allow you to identify and eliminate these new vulnerabilities on an ongoing basis, before they are discovered by cybercriminals.

Finally, penetration testing allows you to keep up with the evolution of attack techniques. Hackers are constantly developing new and creative ways to bypass security. Ethical hackers who are professionally involved in security keep abreast of these trends and use the latest attack techniques during testing. As a result, pentest provides a realistic assessment of resilience to threats that are relevant to the “here and now,” not just those known a few years ago.

What IT infrastructure components (networks, servers, applications) should be tested?

Penetration tests can cover virtually any element of a company’s IT infrastructure. The scope of the test should always be tailored to the specifics of the organization, its key resources and identified risks. Most often, several key areas are tested.

1. external network infrastructure: These are tests targeting those elements of a company’s network that are visible from the public Internet. The goal is to see if an outside attacker can find a point of attack and infiltrate the internal network. Company firewalls, VPN servers, mail servers, web servers and any other services exposed to the world are tested. Pentesters scan ports, look for vulnerabilities in network services and try to bypass edge security.

2 Internal network infrastructure: These tests simulate a situation in which an attacker has already gained access to the company’s internal network (e.g. by infecting an employee’s laptop or as a guest on a Wi-Fi network). The goal is to see how easily a hacker can move around the network (known as “lateral movement”), escalate privileges and gain access to critical resources such as domain controllers, file servers or databases.

3. web and mobile applications: This is one of the most common testing targets. Pentesters analyze applications (e.g., an online store, a customer panel, an e-banking system) for vulnerabilities specific to this environment, such as those on the OWASP Top 10 list (e.g., SQL Injection, Cross-Site Scripting (XSS), CSRF). They test both the logic of the application itself and the security of its APIs.

4 Wireless networks (Wi-Fi): These tests are designed to verify the security of corporate Wi-Fi networks. Pentesters try to crack passwords to the network, bypass security, and verify that the guest network is properly isolated from the internal network.

5 – Social engineering tests: In this case, the target is not technology, but people. Ethical hackers conduct controlled phishing attacks or manipulation attempts to assess employees’ security awareness.

What does a professional penetration test look like step by step?

A professional penetration test is a structured project that follows a proven, multi-step methodology. This ensures that the entire process is comprehensive, repeatable and secure.

Phase 1: Planning and scoping agreement. This is a key formal step. Before starting any activities, pentesters, together with the client, precisely define the scope of the test (which IP addresses, domains, applications will be tested), the objectives (e.g. “gain access to the customer database”), the timeframe and the rules of conduct (e.g. at what hours the tests can be conducted, how to proceed if a critical vulnerability is detected). All these arrangements are recorded in a formal contract.

Phase 2: Reconnaissance (information gathering). In this phase, pentesters, like real hackers, try to gather as much information about the target as possible using OSINT (open source intelligence) and active scanning techniques. They identify IP addresses, running services, software versions and even employee email addresses.

Phase 3: Vulnerability scanning and analysis. Based on the information gathered, pentesters use specialized tools to scan the target for known technical vulnerabilities and configuration errors.

Phase 4: Exploitation (vulnerability exploitation) trial. This is the heart of a penetration test. In this phase, ethical hackers attempt to actively exploit (exploit) the security vulnerabilities found to gain unauthorized access, escalate privileges or perform another action defined in the test objectives. This phase requires a great deal of knowledge, creativity and experience.

Phase 5: Post-exploitation. If they manage to gain access, pentesters investigate how far they can go inside the attacked system or network, trying to reach the most valuable resources. All activities are, of course, controlled and do not destroy data.

Phase 6: Reporting and Recommendations. Once testing is complete, all findings, attacks conducted and their results are documented in detail in a comprehensive report. The report includes not only a description of the vulnerabilities, but more importantly an assessment of their risk and specific, practical recommendations for their remediation.

What to look for when choosing a company that offers ethical hacking services?

Choosing the right company to conduct penetration testing is a key decision that directly affects the quality and value of the entire project. Entrusting access to one’s infrastructure to an outside entity requires a great deal of trust. Therefore, when choosing a partner, it is important to pay attention to several key aspects.

1 Team experience and certifications: The most important asset of a pentester company is its people. You should check what experience and, very importantly, what internationally recognized industry certifications the people who will be conducting the test have. Some of the most prestigious certifications in the field include OSCP (Offensive Security Certified Professional), OSCE, CEH (Certified Ethical Hacker) or certifications from the SANS Institute. Having such certifications is proof of high, verified technical competence.

2 Methodology and Transparency: a professional company should operate on a structured, proven methodology (e.g., based on standards such as PTES or OSSTMM). Before signing a contract, the company should transparently outline how the entire process will work, what tools will be used and how it will communicate with the client during testing.

3 Reporting quality: Ask for a sample, anonymized penetration test report. This is the company’s showcase. A good report is not just a list of bugs found. It must be understandable to both technical people and management. It should include a summary for management, a detailed technical description of each vulnerability, an assessment of its risk in a business context and, most importantly, specific and practical recommendations for fixing the problem.

4 Insurance and legal aspects: Make sure the company has adequate liability insurance (third-party liability) in case an unforeseen failure occurs during the controlled activities. The contract must precisely regulate confidentiality, the scope of testing and the responsibilities of both parties.

What information should a comprehensive test report contain to be useful to the business?

The penetration test report is the most important “product” of the entire service. It is on its basis that the company will make investment decisions and plan corrective actions. To be fully useful, it must be more than just a technical list of errors. It must translate technical risks into understandable business language.

A good report should consist of several key sections: 1. Executive Summary: This is the most important section for management and non-technical people. It should succinctly, without technical jargon, describe the overall security status, the most important risks found and their potential impact on the business. It should also include general, strategic recommendations and a summary of whether the test objectives were met.

2 Description of scope and methodology: This section should accurately describe what was tested (IP scope, applications), when it took place, and what methodology and tools were used. This ensures transparency and reproducibility of the process.

3 A detailed technical description of the vulnerability: This is the heart of the report for the technical team. Each vulnerability found should be described in a separate section and include:

• Name and classification (e.g., according to OWASP Top 10).
• Risk assessment (e.g., critical, high, medium, low), based on likelihood of use and potential impact.
• A detailed description of the vulnerability and the steps to reproduce it (Proof of Concept), often with screenshots.
• Specific and practical recommendations for fixing the vulnerability (e.g., suggestions for code changes, configuration recommendations, links to documentation).

4 Summary and Conclusions: The report should close with a summary section that collects key findings and helps prioritize corrective actions, indicating which vulnerabilities should be patched first.

How to prioritize and plan corrective actions based on the pentest results?

Receiving a penetration test report, often containing a long list of vulnerabilities, can be overwhelming. The key to effective action is a methodical approach to prioritizing and planning remediation efforts. The goal is to focus first on those vulnerabilities that pose the greatest real risk to the organization.

The primary prioritization tool is the risk score assigned to each vulnerability in the report. A professional report should classify each vulnerability based on a standard risk matrix, taking into account two factors: the probability of exploitation (how easy it is to find and attack) and the potential business impact (what would be the consequences of exploitation – e.g., data loss, business interruption, financial loss). Vulnerabilities classified as critical and high must absolutely be patched first and as soon as possible.

The corrective action planning process should look like this:

1. Analysis of the report: The technical team and business representatives should review the report together to ensure that they fully understand the identified risks and their implications.
2. Create a remediation plan: For each vulnerability, starting with the highest priority ones, create a specific task in a project management system (e.g. Jira). The task should include a description of the problem, a recommendation from the report, and should be assigned to a specific person or team responsible for fixing it.
3. Establish deadlines: For each task, set a realistic but challenging deadline (Service Level Agreement, SLA), e.g. critical vulnerabilities – 7 days, high vulnerabilities – 30 days, medium vulnerabilities – 90 days.
4. Tracking progress: The project manager or safety officer should regularly monitor the progress of the remediation plan and report it to management.

Once patches have been deployed for the most important vulnerabilities, a key step is to conduct a re-test, i.e. a re-verification by a pentester that the vulnerabilities have been successfully addressed and that the patch itself has not inadvertently introduced new problems.

How often should penetration tests be repeated to keep up with new threats?

Penetration testing is not a one-time event, but part of an ongoing security management cycle. In a dynamic environment, where new threats are emerging and IT infrastructure is constantly changing, a one-time test quickly becomes obsolete. Regularity in pentesting is key to maintaining a high level of resilience.

The frequency of testing depends on several factors, such as company size, industry, regulatory requirements and risk level. However, there are some generally accepted best practices. For most organizations, the standard is to conduct a comprehensive penetration test at least once a year. Such an annual cycle allows for systematic verification of the state of security and identification of new vulnerabilities.

However, in many cases, an annual test is not enough. Pentests should also be conducted after any major change in infrastructure or applications. This could be the deployment of a key new web application, a major ERP upgrade, a migration to the cloud or a significant change in network architecture. Any such change can inadvertently open up new vulnerabilities that should be verified before they are discovered by attackers.

For companies with a very high level of maturity or operating in high-risk industries (e.g., finance, e-commerce), a continuous penetration testing approach is often used. This involves working with a team of ethical hackers on a continuous basis, throughout the year, to try to find weaknesses in systems. This approach, often implemented in the form of “bug bounty” programs or ongoing contracts, provides the highest level of verification and allows the fastest response to newly discovered threats.

How is a penetration test different from a security audit and vulnerability scan?

The terms “penetration test,” “security audit” and “vulnerability scan” are often confused and used interchangeably, but they describe three completely different activities with different goals and scope. Understanding these differences is key to choosing the right service.

Vulnerability Scanning is a fully automated process that involves using specialized software (a scanner) to scan systems or networks for known vulnerabilities. The scanner has a huge database of known vulnerabilities (CVEs) and checks to see if any of them are present in the environment under test. The result is a long list of potential problems. Scanning is fast, cheap and good for regular “hygiene” of systems, but it often generates a lot of false positives and does not verify that the vulnerabilities found are actually exploitable.

Penetration Testing is, as described earlier, a manual and creative process that goes a step further. The pentester not only finds vulnerabilities, but actively tries to exploit them to demonstrate a real risk. Its goal is to simulate an attack and answer the question, “Is the attacker able to break in and what damage can they do?” A penetration test is much deeper, more precise and provides much more valuable, verified information than an automated scan.

Security Audit is yet another activity. It does not focus on technically “breaking” systems, but on verifying an organization’s compliance with a specific standard, policy or regulation. The auditor checks whether the company has adequate documentation, whether it follows defined procedures and whether it complies with the requirements of, for example, ISO 27001, RODO or an internal security policy. The audit answers the question, “Are we doing what we declared we would do?”

What role do social engineering tests play in assessing infrastructure security?

Social engineering testing is a specific but extremely important type of security testing that focuses on the weakest yet most important link in the entire defense system – the human being. Even the best technically secured infrastructure can be compromised if an employee allows himself to be manipulated and voluntarily reveals his password or runs malware. Social engineering tests allow a practical assessment of employee security awareness and the effectiveness of implemented procedures.

The most common form of social engineering testing is controlled phishing campaigns. Ethical hackers, often after prior OSINT reconnaissance, create and send fake but highly credible e-mails to company employees that attempt to get them to perform a specific action – for example, to click on a link leading to a fake login page in order to extort credentials, or to open an “infected” attachment that is actually a harmless tracking file.

Other forms of social engineering testing can include vishing (phishing attempts over the phone) or even physical testing, where a pentester attempts to enter a company’s office, posing as a courier or service technician, to test the vigilance of employees and the effectiveness of physical access controls.

The purpose of these tests is not to stigmatize or punish employees who have been fooled. The goal is to gather objective data on the level of awareness in the organization. The test results – for example, the percentage of employees who clicked on a phishing link or gave out their password – are invaluable feedback. They allow you to identify which departments or groups of employees need additional, targeted training, and to measure the effectiveness of your security awareness program over time.

How will a penetration testing service from nFlo help you discover weaknesses in your infrastructure and get specific recommendations on how to fix them?

At nFlo, we approach penetration testing as a key part of a partnership that aims to realistically and measurably strengthen your company’s security. Our service is much more than just automated scanning – it’s a process conducted by certified, experienced ethical hackers who think and act like real cybercriminals to provide you with knowledge you won’t get any other way.

Our process begins with an in-depth understanding of your business and your risks. We work with you to define the scope and objectives of the tests, focusing on the elements of your infrastructure that are most critical to your business. Whether the target is your external network, a web application or your employees’ resistance to phishing, we tailor our methodology to your unique needs.

During testing, our specialists use the latest techniques and tools to simulate advanced attack scenarios. We don’t stop at finding the first vulnerability – we try to exploit it to show how far an attacker could go and what data they could access. Our goal is to demonstrate the real business impact of the identified vulnerabilities.

The most important product of our work is a comprehensive and understandable report. We do not leave you with a technical list of problems. We describe each vulnerability we find in detail, its risk is assessed in the context of your business, and most importantly, we provide specific, practical and ready-to-implement recommendations for remediation. Once the testing is complete, our team is available to discuss the results, answer your technical team’s questions, and help you plan remediation efforts. When you work with nFlo, you invest not in a report, but in real security and peace of mind.