Penetration testing: The complete guide from cybersecurity professionals

Penetration testing: The complete guide from cybersecurity professionals

Ideally, any corporation should strive to develop a strong and layered cybersecurity system. However, security gaps begin to emerge at different stages of the cybersecurity process and depend on a variety of factors, like design errors (which are usually the most significant contributors to security gaps), incorrect configuration and settings of related hardware and software, network connectivity issues, human factor whether intentional or not, miscommunication, and, of course, lack of cybersecurity awareness and training.

In this article we are going to look at security from the perspective of a malicious actor with capabilities to exploit any of the mentioned factors. This approach is known as penetration testing, which is performed as a service and in good faith.

What is penetration testing?

Penetration testing or pentesting is one of several techniques for identifying areas of a system vulnerable to intrusion, that is compromise of integrity and authenticity by unauthorized and malicious users or entities. Pentesting covers internal and external perimeters. The penetration testing process involves intentional agreed attacks on a system that can identify both its weakest areas and gaps in security against third-party intrusions, and thereby improve the overall security posture.

This technique can also be used as a complement to other testing methods to evaluate the effectiveness of a system's defense portfolio against various types of unexpected malicious attacks, like vulnerability assessment.

Penetration testing is a real-time, assessment, manual or automated test. The system and its associated components are exposed to simulated malicious attacks to identify security gaps.

While vulnerability assessment follows a predefined and established procedure, penetration testing is out to solve one problem only, which is to destroy the system regardless of the approaches adopted. Much like a real attacker, the pentesters’ job is to compromise a given system, and it does not ultimately matter how they go about doing it.

Is penetration testing necessary?

A typical company that would use the services of penetration testing specialists is a large company that has a fairly mature information security system.

The company is likely to be operating several software products: client and internal corporate applications, mobile apps, and other mobile applications. A good example is any of the Russian big five banks. True, in their case, pentesting is not only a vital necessity, but also a legal obligation.

What is the purpose of penetration testing?

Pentesting can be roughly classified as one of the legal forms of ethical hacking. As stated earlier, security gaps provide an unauthorized user or illicit entity with the opportunity to attack the system, affecting its integrity and confidentiality. Thus, penetration testing helps get rid of these vulnerabilities and enables the system to defend against expected and even unexpected malicious threats and attacks.

Let's consider the results of this technique in more detail. Penetration testing provides the following:

  • A way to identify weak and vulnerable areas of the system before a hacker even notices them. Frequent and sophisticated system updates can affect corresponding hardware and software, leading to security problems.
  • The ability to evaluate a system's existing security mechanism. This allows developers to assess their security competence and maintain the level of security standards defined for the system. This helps organizations to evaluate whether to mitigate or completely eliminate various business risks and issues.
  • A tool to identify and meet certain core security standards, regulations, and practices.

Thus, we see that a company has a lot to gain from this type of assessment, hence the stable year-on-year growth of penetration testing services around the world.

Why is pentesting important?

Penetration testing is necessary to show the true consequences of an attack on a business IT environment. Penetration testing is a simulation of a potential attacker's actions in order to assess the probability of unauthorized access to the corporate information system and to demonstrate the vulnerabilities existing in the information security system. This type of assessment is crucial for organizations as it creates many opportunities for companies to be better prepared for attacks. Let’s look into some of the opportunities that penetration testing can afford us.

Identify and prioritize security risks

With penetration testing, an organization can assess its ability to protect its users, endpoints, networks, and applications from internal or external attempts to bypass the existing security controls, and eventually resulting in unauthorized access to protected assets.

Intelligently manage vulnerabilities

Pentesting provides insight into actual exploitable security threats. Regular testing allows companies to form a proactive action plan regarding which vulnerabilities are most critical, which are of lesser significance, and which are mere false positives. Thus, a company can apply an intelligent spin to prioritizing remediation, patching, and resource allocation.

Leverage a proactive security approach

As of now, there is no single panacea solution to prevent a compromise. The current trend is all about the reach and quality of the portfolio of defensive mechanisms, including encryption, antivirus, SIEM, and IAM, to name just a few. However, even the best security portfolio is not a guarantee that a company will be able to locate and eliminate all vulnerabilities in their digital environment. But, at least, with the proactive approach offered by penetration testing, companies can form a better picture of their threat landscape and produce a logical action plan to minimize possible vulnerabilities.

Verify existing security programs

Penetration testing gives companies a glimpse into their weaknesses, but not only that. They also serve as quality assurance for the security systems that do work — something that companies can take into account when evaluating their internal policies or specific tools.

Become more confident in your security strategy

What gives companies the most confidence in their security portfolio? Is it the amount of money invested or its performance during testing? Certainly, an expensive and flashy portfolio with all the latest and coolest solutions is a coveted goal, but the only way to truly find out how well prepared a company is for real threats is through penetration testing.

Meet regulatory requirements

Another reason for why pentesting is important, as mentioned above, is the legally binding aspect of it. These days companies are held accountable for the level of security they have instated. So, in order to avoid government fines, it is advised that penetration testing is never put on the back burner. Failure to comply with regulations entail some bitter fines, hence most of the companies with a respectable security posture do not hesitate to allocate the required resources towards penetration testing.

5 stages of penetration testing

To perform penetration testing of an IT perimeter, a consistent standard approach is used, which includes the steps featured further in this section.

Planning and reconnaissance

This step includes gathering requirements, defining the scope, strategies, and objectives of penetration testing in accordance with the existing security standards. Followed by the collection and analysis of the most detailed information about the system and related security attributes, used for targeting and attacking each block..In addition, this stage may include an evaluation and listing of the areas to be tested, the types of tests to be performed, and other related checks.


The next step is to understand how the target system will respond to various intrusion attempts. Pentesters identify and locate vulnerable areas of the system, which will later be used to attack the system being tested. Some of the most popular and widely used penetration testing tools include Nmap, Nessus, Metasploit, Wireshark, OpenSSL, Cain & Abel, w3af.

Gaining access

An actual system penetration test that includes internal and external attacks, using cross-site scripting, SQL, injections, and backdoors. External attacks are simulated attacks from the outside that prevail outside the system/network boundary (e.g., gaining unauthorized access to system functions and data related to applications and servers addressed to the public). Internal attacks originate after a successful intrusion of authenticated objects into the system or network, and aim for different operations (when compromising the integrity and reliability of the system), which can intentionally or unintentionally compromise the system.


In the effort to imitate the actions of a real attacker, the aim here is to achieve a persistent presence in the exploited system through a discovered vulnerability. Bad actors tend to use this approach to go into hiding once the target system has been compromised. By concealing themselves within the perimeter, hackers can quietly gain in-depth information about the system, sometimes over months of being undetected, and plan more ferocious campaigns.


Reporting includes documentation of the activities carried out in all of the stages mentioned. In addition, it can describe the various risks, the problems identified, the vulnerable areas (used or not), and the solutions proposed to address the weaknesses.

5 penetration testing methods

Penetration testing usually has three standard approaches from the point of view of the tester: black box, where the tester has zero knowledge about the system (testing as an attacker), white box, where the tester has full knowledge about the system (testing as a developer), gray box, where knowledge about the system is limited (testing as a user with access to some data). All three of these approaches can be applied to the various scenarios below for a different result.

External testing

External pentesting is aimed at the company’s assets that are visible on the Internet, such as a web application, website, email and domain name servers. The goal here is to gain access from the outside of the company’s perimeter and extract business-valuable information.

Internal testing

This method is designed to test company security from a potential malicious insider attack from behind the company’s firewall. This does not necessarily mean that the test is aimed at identifying some bad apples among the employees. Their credentials could have been obtained through a phishing attack.

Blind testing

Blind testing involves a tester who’s been given only the name of the target organization. This gives the security team a real-time insight into how an actual attack would perspire.

Double-blind testing

Much like the previous method, only in this scenario both the attacker and the security department have little knowledge about each other's activities. This method very closely resembles a real-life situation.

Targeted testing

In this case, the tester and the security department work together and keep each other abreast regarding one another’s activities. The value in this approach is that it gives the security department the necessary feedback from the hacker’s point of view.

Different types of pentesting

Penetration testing, depending on the elements and objects being tested, can be classified into six types.

Web application tests

Used to detect security breaches and other problems in multiple variants of web applications and services hosted on the client or the server side. While it is true that web applications have some overlap with network services, a web test is far more detailed, deep, and time-consuming.

Network security tests

Network penetration testing to discover and identify the possibility of access by hackers or any unauthorized entity. Network attacks may include circumventing endpoint protection systems, intercepting network traffic, testing routes, stealing credentials, exploiting network services, discovering legacy devices and third-party appliances, etc.


A wireless test is designed to look for vulnerabilities in wireless networks. The test is intended for wireless applications and services, including their various components and functions (routers, filtering packets, encryption, decryption, etc.).


Physical tests are all about gaining physical access to the company premises. Once inside the building, the attacker may try several tricks to get important information. Some of which would be to eavesdrop, hide listening devices or scatter portable media that contain a virus.

Cloud security tests

The test is ideal for cloud-based systems, and the focus of the test is to make sure that the cloud is deployed correctly. This method also helps to identify the overall risk and likelihood for each vulnerability, with recommendations on how to improve your cloud environment.

Social Engineering

This test involves a "human contingent" capable of clearly identifying and receiving sensitive data and other information via the Internet or telephone (this group may include employees of the organization or any other authorized persons present on the organization's network).

How often should a company take a pentest?

A good rule of thumb is to conduct penetration testing no less than once a year. This way companies have a much more manageable workframe. This periodicity is, in fact, mandated by the current legislation and should not be neglected. However, legal mandates are not the only motivation to conduct penetration testing. In addition to regular scheduled assessment, a company should commit to a pentest whenever some changes take place in the infrastructure, such as new applications being added, security patches being applied, any upgrades to the infrastructure, policy adjustments, new office locations.

What happens in the aftermath of a pentest?

After the pentest is finished, the testing specialist drafts a report with the findings. Typically, this is a detailed technical report that contains maximum information about the discovered vulnerabilities, examples of their exploitation, and recommendations to remedy the flaws. The owner of the system then proceeds to follow the recommendations to fix the vulnerabilities, after which the tester comes back to verify the conducted remediation. If all the gaps are subsequently closed — great! If not, the testing specialist woud, generally, offer some support in implementing the recommended counter-measures.


Hackers, armed with advanced technologies with a wide range of resources and tools, often easily break into a system or network with the intent to harm a company's reputation and assets. Penetration testing, more so than other types of testing, can be seen as a tool to identify various security gaps before it is too late, helping to negate potential threats to the system as a whole.


How is penetration testing done?

System penetration testing can be performed using any of the following three approaches: manual testing, automated testing, and a mix of the two.

Is penetration testing worth it?

Certainly so! As was mentioned in the article, penetration testing is mandated by the state which means that any violation of the prescribed testing entails certain fines and penalties, which are best avoided altogether.

When is penetration testing required?

Once a year should do the trick. But remember that penetration testing is recommended whenever any changes are implemented to the infrastructure, such as the introduction of new endpoints or changes in the security controls.

Why do penetration testing?

Pentesting helps companies get a clear picture of their security posture, where they stand in terms of risks and their maturity to handle those risks. Ultimately, pentesting is a way for companies to assess their current security situation and plan ahead for possible improvements.