Penetration Testing: Complete Guide to Process, Types, and Tools

What Is Penetration Testing?

Penetration testing is a way of assessing the security of an computing system or network by exploiting security vulnerabilities. It is carried out by ethical hackers, who use the same techniques as malicious attackers, but without causing damage to the tested system or the organization.

Security flaws can exist in many areas, including insecure system configuration, authentication, known vulnerabilities, and business logic flaws. Penetration testing can identify such flaws, and also test the effectiveness of the organization’s current defenses. The penetration tester’s goal is to demonstrate that an external attacker can identify and exploit a flaw or vulnerability, and show how.

Penetration testing is usually a combination of manual and automated testing. Ethical hackers use a variety of tools to attempt to compromise a tested system—with proper approval and clear definition of the allowed scope of the test. When the hackers discover and exploit vulnerabilities, customers are provided with detailed penetration testing reports with information about the scope of the tests, vulnerabilities found, severity, and remediation recommendations.

Why Is Penetration Testing Important?

Cyber attacks are growing in severity and frequency, and businesses of all sizes are at risk. Only a few examples of severe attacks are ransomware, phishing, and web-based attacks like cross site scripting (XSS) and SQL injection.

Penetration testing uses a hacker's perspective to identify and mitigate cybersecurity risks before they are exploited. Unlike other security testing methods, it discovers proven vulnerabilities, not just alerts that need to be investigated, and demonstrates their business impact. This helps IT and security teams proactively improve their security posture to minimize the chance of a successful attack.

Another element of penetration testing is that skilled ethical hackers use their creativity, combining several attack vectors to find a way into a company’s systems. This is extremely important because attackers will do the same, looking for loopholes and overlooked aspects of security that automated tests can miss.

Penetration Testing vs. Vulnerability Assessments

Vulnerability assessment is a technique that uses automated scanning tools to find network vulnerabilities and list the results in a report. This process generates many false positives rather than reflecting the real-world risk of an exploit.

A major way that vulnerability assessments differ from penetration tests is the breadth and depth of the vulnerability coverage. Vulnerability assessment emphasizes quantity and aims to discover as many faults as possible, providing initial visibility over the threat ecosystem. Penetration testing is better suited for testing a mature security system’s defenses and ensuring they protect the network from attack.

Automation is another difference between the two techniques. While vulnerability assessment typically relies on automated tools, pentesting involves more human expertise, combining automation with manual processes.

Therefore, penetration testing requires more specialized skills than vulnerability assessment. Automated tests don’t require a significant skill set to manage, but hacking techniques require training, experience, and creativity. Many organizations outsource penetration testing workloads to an external service provider rather than relying on in-house specialists.

Penetration Testing vs. Vulnerability Scanning

Both penetration testing and vulnerability scanning techniques can help an organization identify weaknesses in its security strategy. Vulnerability scanning is a subset of security vulnerability assessment that relies heavily on automation and aims to uncover known vulnerabilities quickly. Penetration testing offers a deeper assessment and focuses on identifying complex or unknown vulnerabilities that an automated tool cannot detect. Pentesting also has the added objective of assessing the exploitability of the vulnerabilities.

The tool-based approach of vulnerability scanning is suited to repeatable tasks that help ensure consistency and save time. Penetration tests involve a manual approach that emphasizes creative thinking and mapping out attack techniques. Vulnerability scanners often classify vulnerabilities as high-risk even if attackers are unlikely to exploit them.

Vulnerability scans are useful for identifying publicly known vulnerabilities. They save security teams time by going over vulnerability databases and alert organizations when it’s time to update an application or apply a patch. Pentests also uncover known vulnerabilities, but they focus more on detecting hidden vulnerabilities, including complex code injection, XXS, and social engineering vulnerabilities.

Another important difference is the tools. Vulnerability scanning relies on automated vulnerability assessment tools, while penetration testing usually incorporates multiple, diverse security tools. For example, pentester may use special ethical hacking platforms and custom tools to investigate specific threats (e.g., Python-specific or Java-specific vulnerabilities). The downside of these tools is that they often take a long time to master and are not always easily available.

Penetration Testing Methodologies

Pen tests are generally divided into three categories:

  • Black box — The pen test begins without prior knowledge of or access permissions to the target environment. This type of pen test simulates the actions a malicious actor may perform to breach the target, for example, conducting research and reconnaissance. Black box is considered the most realistic assessment of external threats.

  • Gray box — The pen test has initial, limited knowledge of and authorized access to the target environment. The test may begin with a legitimate user account and an employee-level understanding of the network. This type of pen test simulates an insider threat attack or the actions of a malicious external actor after gaining initial access through compromised credentials, phishing, or other means.

  • White box — The pen tester has full, authorized access to the target and all information and documentation related to the target. This type of pen test is often faster because there is no need to perform reconnaissance. However, admins’ preconceptions about how the system is designed to work may influence the pen tester.

In addition to the above pentesting types, it is also customary to use the following categories when determining the most suitable test to perform:

  • External test — Involves attacking information assets visible to outsiders, such as apps, websites, DNSes, and email. The objective may be extracting data, performing transactions, or other malicious activities. This test can help identify vulnerabilities visible to external attackers.

  • Internal test — Involves launching an internal attack to expose the scope of damage possible internal threats can cause to the tested system. It covers malicious insiders and employees responding to phishing attacks and social engineering.

  • Blind test — Involves obtaining publicly available information about the target. The tester does not get any inside information about the target and its security posture while the target company expects the attack. The company is informed of when and where the attack will occur and can prepare in advance.

  • Double-blind test — Involves launching an attack when neither the pen tester nor target have prior knowledge about the test. It requires testers to rely on available tools and skills to penetrate the target’s defenses. The target company also must rely on its resources to prevent the tester from penetrating its defenses.

What Are the Main Steps of Penetration Testing?

Here are the five steps of penetration testing:

1. Planning

The planning phase involves determining the test’s objectives and performing initial system reconnaissance. The pen tester gathers information during this state, often using social engineering to obtain the data needed to perform the attack.

2. Scanning

The planning phase involves analyzing or scanning the system to determine how it will respond to the attack. Pen testers often use technical tools during this process, performing vulnerability scans and looking for gateways to gain unauthorized access.

3. Breaching

The breaching phase involves using various strategies, such as SQL injection and backdoors, to identify a way to bypass the firewall and breach the system. The pen tester can then breach the system, taking control of devices or the network and extracting data.

4. Burrowing

The burrowing phase involves determining how long the pen tester can stay in the system, identifying data they can compromise, and learning how much deeper the tester can burrow into the system. The pen tester strives to maintain access for as long as possible, often by installing backdoors and planting rootkits.

5. Analyzing

The analyzing phase involves creating a detailed configuration review and reporting the test results. Additionally, the pen testers may simulate how a malicious actor will try to cover their tracks. At the end of the test, the pen tester gathers all the information obtained and reports on exploitable vulnerabilities.

Penetration Testing Tools

Professional penetration testers use a variety of automated tools. The following types tools are commonly used:

  • Port scanner — Identifies open ports on the target system. This helps the tester identify the operating systems and applications running on the network. These tools help provide reconnaissance data and discover new attack vectors.

  • Vulnerability scanner — Identifies known vulnerable applications and misconfigurations on a system. Reports provided by the vulnerability scanner help pentesters select vulnerabilities to exploit for initial access.

  • Network sniffer — Monitors data in network traffic (including encrypted traffic), including where it came from, what device it came from, and what protocol was used. Network packet sniffing can identify suspicious traffic on a network as part of network penetration testing.

  • Web proxy — Allows testers to intercept and tamper with traffic between a browser and an organization’s web servers. This lets testers detect hidden HTML features that represent vulnerabilities such as form fields. These types of vulnerabilities can be used for attacks like cross-site scripting (CSS) and cross-site request forgery (CSRF).

  • Password cracker — Password hashing is a common target for attackers to gain access to the target network. Password crackers allow penetration testers to determine if an organization’s employees use weak passwords that pose a risk of abuse.

Types of Penetration Testing Services

Penetration testing services are applicable at multiple IT infrastructure levels. Here are a few common types of pentest services:

Web App Penetration Testing

Web application penetration testing involves looking for data validation and integrity vulnerabilities, authentication and user session management issues, and more. Penetration testing identifies security issues in web app source code, databases, and back end networks.

Penetration testing of a web application is typically divided into three phases: reconnaissance, discovering vulnerabilities, and attempting to exploit them to gain unauthorized access to applications or backend systems.

Network Penetration Testing

Network penetration testing identifies security vulnerabilities in network infrastructure such as firewalls, switches, and routers, and network-related vulnerabilities in endpoints. This helps prevent attacks that exploit firewall misconfigurations, attacks on switches or routers, and DNS, proxy, and man-in-the-middle (MiTM) attacks.

Network penetration tests use techniques such as port scanning, system fingerprinting, configuration vulnerability assessment, virus and malware scanning, and traffic fuzzing.

API Penetration Testing

APIs play an important role in modern IT systems. Many information systems communicate with APIs or expose them over the public Internet, and exchange sensitive data over those APIs, making them an attractive attack vector for malicious actors.

API penetration tests learn API structures and commands (certain tools can fetch API commands with standards such as OpenAPI) and can identify various security issues including weak authentication, code injection vulnerabilities, resource rate-limiting, and data leaks.

Mobile App Penetration Testing

Many organizations have a Bring Your Own Device (BYOD) policy. This means that the employee’s personal mobile device can connect to the network. These personal devices usually are less secure than enterprise devices.

Mobile application penetration tests can identify new attack vectors, such as the distribution of malware via a mobile application, phishing messages targeting BYOD devices, exploitation of vulnerabilities in a WiFi network, and mobile device management (MDM) protocol violations.

Penetration Testing Best Practices

The following best practices allow organizations to make the most of penetration tests.

Defining the Test Scope

Testing the entire network is rarely practical, given the penetration test cost. Organizations should set their testing budgets and define the scope of their tests to prioritize critical and high-risk parts of the network and applications. For example, code-intensive applications may present a more significant risk and suitable penetration testing targets.

Identifying and Prioritizing Risks

Organizations should identify the areas that pose a greater application security risk. Common sources of application vulnerabilities uncovered by pentesters include operating systems, application code, and config files. For example, attackers can exploit weaknesses in the underlying operating system to control an application’s behavior — security patches can help protect the operating system from attack.

Developers often make errors in the application code, exposing data or impacting performance. Penetration tests can help inform the development team’s policies - for example, by anticipating malicious actions and restricting end-user access. Misconfiguration issues are a similar risk, with many attackers using configuration files to find weaknesses. A secure system should prevent snooping so outsiders cannot access config files.

Incorporating Diverse Data Sources into the Penetration Tests

Data is an organization’s biggest asset, including financial and customer data. Organizations with sensitive data should conduct full penetration tests on the data sources to ensure regulatory compliance. The tests should also cover the connecting software.


Once an organization chooses the areas that need testing, it must prepare for the penetration tests. The organization must know what types of tests the cloud vendor supports, build a test review and response team, and schedule automated patches after each test. Changes made during pentesting can affect the results.

Employing Security Services

A major obstacle to establishing an effective security strategy is finding the right personnel. Many organizations cannot directly employ ethical hackers and security specialists, so it makes sense to outsource some responsibilities to a service provider. Regular penetration testing is expensive, but it can help prevent issues later. Professional pentesting services allow customers to access valuable expertise and are often more affordable than employing an in-house pentesting team.

Penetration Testing with BlueVoyant

Today’s security teams need to adopt a proactive approach to protecting client networks, products, and personnel from malicious attacks. BlueVoyant utilizes industry-standard methodologies, focusing on the adversarial mindset to identify vulnerabilities and exploitation vectors to provide clear and concise remediation recommendations.

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