What is Penetration Testing—Types, Tools & Best Practices

Penetration testing is a type of security practice that enables companies to stay ahead of potential cybersecurity threats, like malware, social engineering, phishing, and DDoS attacks.

Cybersecurity threats are more pervasive and sophisticated than ever—and they’re happening more often than you might think. In fact, a study from Cybersecurity Ventures revealed that in 2023, a cyberattack occurred every 39 seconds. 

Furthermore, these hacks and breaches are affecting a lot of companies, big and small. According to the 2024 Cisco Cybersecurity Readiness Index, 54% of companies have experienced a cybersecurity incident in the past year—including T-Mobile (twice), Caesars Entertainment, and MoveIT. Some more recent victims of cyberattacks and data breaches include AT&T, Frontier Communications, and Roku—all occurring in the first half of 2024. These figures and attacks demonstrate the importance of security testing and penetration testing.

In this blog post, we will explore penetration testing in detail—discussing what it is, how it’s done, why it’s important, and look at tools, types, stages, methodologies, and examples.

Let’s get started.

Jump to:

• What is penetration testing?
• Why is penetration testing important?
• What gets tested in penetration testing?
• Types of penetration testing
• Penetration testing stages
• Penetration testing methodologies
• Penetration testing tools
• Penetration testing best practices
• Key takeaways

What is penetration testing?

Penetration testing—or pen testing—is a simulated cyber attack against a computer system, network, or web application to uncover security weaknesses. The primary goal is to uncover potential security weaknesses that could be exploited by malicious actors.

Why is penetration testing important?

Penetration testing plays a critical role in maintaining the security and integrity of an organization’s digital assets. Here are several key reasons why penetration testing is important:

Identifying vulnerabilities 

Penetration testing helps organizations discover both known and unknown security vulnerabilities in their systems, networks, and applications. By proactively identifying these weaknesses, companies can address them before attackers have the opportunity to exploit them.

Protecting sensitive data 

Penetration testing ensures that personal, financial, and proprietary information remains secure. This demonstrates a company’s commitment to security and can build trust with customers, partners, and stakeholders.

Complying with regulations 

Many regulatory standards and compliance frameworks require regular penetration testing as part of their security requirements. This includes standards like PCI DSS, HIPAA, and GDPR. It is also a requirement for the ISO 27001 compliance and certification.

Testing security controls 

Penetration testing evaluates the effectiveness of an organization's security controls, such as firewalls, intrusion detection systems, and access controls. It helps validate whether these controls are configured correctly and are capable of defending against real-world threats.

Improving security posture 

By simulating real-world attacks, penetration testing provides valuable insights into an organization’s security posture. It highlights areas of strength and identifies gaps that need improvement, helping organizations enhance their overall security framework and resilience against cyber threats.

Cost savings 

According to a 2023 study by IBM, the average cost of a data breach was $4.45 million. Regular penetration testing can help mitigate such risks and prevent significant financial losses associated with data breaches, regulatory fines, or loss of reputation.

What gets tested in penetration testing?

Penetration testing is a comprehensive process designed to identify and exploit vulnerabilities across various components of an organization’s IT infrastructure.

Here’s a look at the key areas that are typically assessed during penetration testing:

1. Network infrastructure

External network

• Firewalls and routers. Testing for misconfigurations, open ports, and weaknesses in filtering rules.
• Public-facing servers. Assessing web, email, and other externally accessible servers for vulnerabilities.
• Network services. Scanning for vulnerabilities in DNS, FTP, SSH, and other network services.

Internal network

• Internal servers. Testing file servers, database servers, and application servers for vulnerabilities.
• Workstations and endpoints. Evaluating the security of desktop and laptop computers used by employees.
• Network segmentation. Checking for weaknesses in the segmentation and isolation of different network zones.

2. Web applications

Web application vulnerabilities

• Injection flaws. Testing for SQL injection, command injection, and other injection attacks.
• Cross-site scripting (XSS). Assessing the potential for XSS attacks, which can lead to data theft and session hijacking.
• Cross-site request forgery (CSRF). Ensuring that web applications are protected against CSRF attacks.
• Authentication and authorization. Evaluating the strength of login mechanisms and access control measures.
• Session management. Checking for weaknesses in session handling, including session fixation and hijacking.

API security

• Endpoint testing. Assessing the security of API endpoints for unauthorized access and data leakage.
• Rate limiting. Ensuring that APIs are protected against abuse through rate limiting and throttling mechanisms.
• Data validation. Testing input validation and sanitization to prevent injection attacks and data corruption.

3. Mobile applications

Mobile app vulnerabilities

• Platform-specific flaws: Identifying vulnerabilities specific to iOS, Android, or other mobile platforms.
• Data storage security. Ensuring that sensitive data is securely stored and protected on the device.
• Network communication. Testing the security of data transmitted between the app and backend servers.
• Authentication and authorization. Evaluating the robustness of login and access control mechanisms within the app.

Backend services

• API security. Assessing the security of APIs used by the mobile app to communicate with backend services.
• Server-side validation. Ensuring that server-side validation and processing are secure against common attacks.

4. Wireless networks

Wireless network security

• Access points. Testing the security of wireless access points and configurations.
• Encryption Protocols. Evaluating the strength of encryption protocols (WEP, WPA, WPA2, WPA3) used to secure wireless communication.
• Rogue access points. Detecting unauthorized access points that could be used for attacks like man-in-the-middle (MitM).

5. Social engineering

Phishing

• Email phishing. Simulating phishing attacks to evaluate the effectiveness of employee awareness and email security measures.
• Spear phishing. Conducting targeted phishing attacks to test the security awareness of high-value targets within the organization.

Physical security

• Tailgating. Testing physical access controls by attempting to gain unauthorized entry to secure areas.
• USB drops. Distributing malicious USB drives to test the likelihood of employees connecting unknown devices to the network.

6. Cloud Security

Cloud infrastructure

• Configuration security. Assessing the security of cloud configurations, including storage buckets, virtual machines, and security groups.
• Access controls. Evaluating the effectiveness of identity and access management (IAM) policies and practices.

Cloud services

• Service vulnerabilities. Testing cloud services for common vulnerabilities, such as insecure APIs, weak authentication, and misconfigurations.
• Data protection. Ensuring that data stored and processed in the cloud is adequately protected through encryption and access controls.

7. Physical security

Building access

• Physical entry points. Testing the security of doors, windows, and other entry points.
• Security guards and surveillance. Evaluating the effectiveness of on-site security personnel and surveillance systems.

Hardware security

• Device access. Ensuring that sensitive hardware, such as servers and network devices, is physically secured against unauthorized access.

Types of penetration testing

External testing

External penetration testing focuses on assessing an organization's externally-facing assets, such as web applications, websites, and external servers. This type of testing simulates an attack launched from outside the organization's network, similar to how an external threat actor would target the organization. 

Key benefits:

• Identifies vulnerabilities that can be exploited over the internet.
• Tests the effectiveness of perimeter defenses like firewalls and intrusion prevention systems.

Internal testing

Internal penetration testing mimics an attack that originates from within the organization's internal network. This type of testing is useful for identifying vulnerabilities that could be exploited by employees, contractors, or other trusted insiders who have access to the internal network.

Key benefits:

• Assesses the security posture from an insider’s perspective.
• Tests the effectiveness of internal security controls and segmentation.

Black box testing

In black box testing, the penetration tester has no prior knowledge of the target system. This approach simulates the perspective of an external attacker who has little or no information about the organization’s network and infrastructure.

Key benefits:

• Provides a realistic simulation of an external cyber attack.
• Tests the ability to gather intelligence and assess vulnerabilities from scratch.

White box testing 

White box testing, in contrast to black box testing, gives the penetration tester full knowledge of the target system. This includes detailed information about the network architecture, source code, and other technical details that are typically available to an internal IT team.

Key benefits:

• Allows for a more thorough assessment of vulnerabilities.
• Tests the effectiveness of internal security measures and configurations.

Gray box testing 

Gray box testing blends elements of both black box and white box testing. The penetration tester has partial knowledge of the target system, typically including some network diagrams, system configurations, or other relevant information.

Key benefits:

• Mimics the perspective of an attacker who has obtained some insider knowledge or through reconnaissance.

Targeted testing 

Targeted testing, also known as focused testing, involves collaboration between the penetration testing team and the organization’s internal IT team. The goal is to assess specific high-value assets or systems within the organization, with both parties working together to maximize the test’s effectiveness.

Key benefits:

• Focuses on critical areas and assets that are most likely to be targeted by attackers.
• Facilitates knowledge sharing and collaboration between the testing team and internal IT staff.

Blind testing 

Blind testing, similar to black box testing, involves no prior knowledge of the target systems. However, unlike black box testing, it’s conducted without the knowledge of the internal security team. This type of testing provides a more realistic simulation of an external attack.

Key benefits:

• Tests the organization’s ability to detect and respond to unauthorized activities without prior warning.
• Identifies blind spots in the organization’s detection and response capabilities.

Double-blind testing

Double-blind testing, also known as complete testing, takes blind testing one step further. In this approach, neither the organization’s internal IT team nor the penetration testing team is aware of the test. This type of testing provides the most realistic assessment of an organization’s ability to detect and respond to an attack.

Key benefits:

• Offers the highest level of realism in testing the organization’s defenses.
• Assesses the effectiveness of incident response and detection capabilities under real-world conditions.

Penetration testing stages

A comprehensive penetration test typically follows these stages: 

Stage 1: Planning

Planning and reconnaissance is the initial phase of a penetration test. During this stage, the objectives and scope of the test are defined, and relevant information about the target is gathered.

Key activities:

• Defining scope. Determine the systems, networks, applications, and specific areas to be tested.
• Setting objectives. Establish clear goals for the test, such as identifying specific types of vulnerabilities.
• Information gathering. Collect data about the target using various methods, such as DNS enumeration, network mapping, and social engineering. This phase is also known as footprinting and involves both active and passive reconnaissance.

Stage 2: Scanning 

In the scanning phase, the tester uses various tools to identify potential entry points and vulnerabilities within the target systems.

Key activities:

• Network scanning. Identify open ports, services, and live hosts using tools like Nmap.
• Vulnerability scanning. Detect known vulnerabilities in systems and applications using automated scanners like Nessus.
• Enumeration. Extract detailed information about network resources, user accounts, and shares.

Stage 3: Gaining access 

The gaining access phase involves exploiting identified vulnerabilities to gain unauthorized access to the target systems. This stage tests the effectiveness of security defenses and identifies potential attack vectors.

Key activities:

• Exploitation. Use exploit tools and techniques to gain control of the target system. Tools like Metasploit can be used to automate this process.
• Privilege escalation. Attempt to gain higher levels of access within the system to maximize the potential impact of the attack.

Stage 4: Maintaining access 

In the maintaining access phase, the tester aims to ensure persistent access to the compromised system. This stage simulates the actions of an attacker who wants to maintain a foothold within the network for extended periods.

Key activities:

• Installing backdoors. Deploy malware or backdoors that allow re-entry into the system.
• Covering tracks. Use techniques to evade detection and remain undetected within the network.

Stage 5: Analysis and reporting 

The analysis and reporting phase involves documenting the findings of the penetration test and providing actionable recommendations for remediation.

Key activities:

• Data analysis. Review the results of the penetration test to identify patterns and insights.
• Reporting. Create a detailed report that includes an executive summary, technical findings, risk assessments, and recommended mitigation strategies. The report should be clear and understandable for both technical and non-technical stakeholders.

Key elements of the report:

• Executive summary. High-level overview of the test objectives, scope, and key findings.
• Technical details. In-depth analysis of vulnerabilities, exploits used, and the impact of successful attacks.
• Risk assessment. Evaluation of the severity and potential impact of identified vulnerabilities.
• Recommendations. Actionable steps for remediation, including patching, configuration changes, and improvements to security policies and procedures.

By following these stages of penetration testing, organizations can ensure a comprehensive assessment of their security posture, identify weaknesses before they can be exploited, and take proactive measures to enhance their defenses. 

Penetration testing methodologies

Penetration testing methodologies provide a structured approach to conducting penetration tests, ensuring that the process is thorough, consistent, and effective. Here’s a detailed look at some of the most widely recognized penetration testing methodologies:

1. Open Source Security Testing Methodology Manual (OSSTMM)

The OSSTMM is a comprehensive methodology for evaluating the operational security of various domains, including physical locations, workflows, human security, physical security, wireless security, telecommunication security, data networks, and compliance.

Advantages of OSSTMM:

• Provides a detailed and rigorous framework for testing.
• Covers a wide range of security domains.
• Emphasizes the measurement and quantification of security.

2. Open Web Application Security Project (OWASP)

The OWASP is one the most widely recognized standards in the industry, providing a set of methodologies used for web application penetration testing (OWASP Top 10), mobile application penetration testing (OWASP Mobile Top 10), API penetration testing (OWASP API Security Top 10), IoT penetration testing (OWASP IoT Top 10), and LLM penetration testing. 

Advantages of OWASP:

• Widely recognized and respected in the industry.
• Provides practical guidance and tools for web application testing.
• Regularly updated to reflect emerging threats and vulnerabilities.

3. Penetration Testing Execution Standard (PTES)

The PTES provides a standardized framework for conducting penetration tests. It describes seven phases: pre-engagement interactions, intelligence gathering,

threat modeling, vulnerability analysis, exploitation, post-exploitation, and reporting. The framework provides detailed guidance on each phase.

Advantages of PTES:

• Provides a comprehensive and structured approach to penetration testing.
• Covers all phases of the penetration testing life cycle.
• Emphasizes the importance of communication and collaboration with the client.

4. Information Systems Security Assessment Framework (ISSAF)

The ISSAF is a detailed framework for conducting security assessments, including penetration testing. It provides guidance on various aspects of security testing, from planning to execution and reporting.

Advantages of ISSAF:

• Provides a detailed and comprehensive framework for security assessments.
• Covers a wide range of security domains and testing techniques.
• Emphasizes the importance of thorough documentation and reporting.

Penetration testing tools

Penetration testing relies heavily on a variety of tools designed to identify vulnerabilities, exploit weaknesses, and assess the overall security posture of an organization. Let's go through some of the most widely used penetration testing tools, categorized by their primary functions:

1. Reconnaissance and information gathering 

Nmap

A powerful network scanning tool that discovers hosts and services on a network. It has port scanning, OS detection, version detection, and scripting capabilities. Nmap is widely used to map network topology and identify open ports and services.

Recon-ng

A web reconnaissance framework with a modular design, similar to Metasploit. It has modules for gathering information from public sources, including social media, search engines, and DNS. Recon-ng is ideal for collecting and analyzing information during the reconnaissance phase.

2. Vulnerability scanning

Nessus

A comprehensive vulnerability scanner that identifies security vulnerabilities in systems and applications. It offers automated scanning, detailed reports, and extensive plugin support for various vulnerability checks. Nessus is commonly used to detect vulnerabilities, misconfigurations, and missing patches.

OpenVAS

An open-source vulnerability scanning and management solution with an extensive plugin library, detailed reports, and regular updates. OpenVAS is ideal for conducting thorough vulnerability assessments in various environments.

3. Exploitation

Metasploit Framework

A powerful penetration testing framework that provides tools for discovering, exploiting, and validating vulnerabilities. It has an extensive exploit library, payload generation, and post-exploitation modules. This tool is widely used by penetration testers to automate the process of exploiting known vulnerabilities.

BeEF (Browser Exploitation Framework)

A penetration testing tool that focuses on web browser vulnerabilities. Some of its features include exploitation of client-side vulnerabilities, browser hijacking, and social engineering tools. BeEF is effective for testing the security of web applications and assessing browser-based attacks.

4. Password cracking

John the Ripper

A fast and versatile password cracking tool that supports a wide range of hashing algorithms and password attack techniques. John the Ripper is commonly used to crack passwords from hashed password files and assess password strength.

Hashcat

A highly efficient password recovery tool that utilizes GPU acceleration and supports numerous hash algorithms, including MD5, SHA-1, and bcrypt. It is ideal for performing large-scale password cracking tasks quickly and efficiently.

5. Wireless network testing

Aircrack-ng

A suite of tools for auditing wireless networks. Some of its features include packet capture and analysis, WEP and WPA/WPA2-PSK cracking, and network monitoring. It is used to test the security of wireless networks and assess the strength of encryption protocols.

Kismet

A wireless network detector, sniffer, and intrusion detection system. It offers passive network discovery, packet capture, and support for various wireless protocols. Kismet is ideal for monitoring wireless network activity and detecting unauthorized access points.

6. Web Application Testing

Burp Suite

A comprehensive web vulnerability scanner and testing platform. It has a proxy server for intercepting and modifying web traffic, automated scanning, and various testing tools. Burp Suite is widely used for testing web application security, including SQL injection, XSS, and other vulnerabilities.

ZAP (Zed Attack Proxy)

An open-source web application security scanner that offers automated scanning, manual testing tools, and a proxy for intercepting web traffic. It is ideal for finding and exploiting security vulnerabilities in web applications.

7. Post-Exploitation

Empire

A post-exploitation framework for Windows, macOS, and Linux. It has PowerShell and Python agents, modular design, and various post-exploitation tools. Empire is effective for maintaining access and executing commands on compromised systems.

Cobalt Strike

A threat emulation platform used for post-exploitation activities that offers collaboration tools, payload generation, and post-exploitation modules. It is used to simulate advanced persistent threats (APTs) and assess the effectiveness of incident response capabilities.

Penetration testing best practices

Define clear objectives and scope

Clearly define what you aim to achieve with the penetration test, like evaluating the effectiveness of existing security measures or identifying a certain number of vulnerabilities. Also, establish the scope of testing by specifying which systems, applications, and network segments should be tested, as well as identifying exclusions and testing boundaries.

Obtain necessary permission

Ensure that you have the necessary authorization and documentation to conduct the penetration test. Make sure to sign NDAs to protect sensitive information discovered during the test.

Assemble a skilled team

Engage penetration testers who hold relevant certifications and have experience in conducting penetration tests in similar environments and industries. 

Follow an efficient approach

Utilize established penetration testing frameworks, keep detailed logs of all activities performed during the penetration test, and document all findings with supporting evidence.

Communicate effectively

Provide regular updates to stakeholders on the progress of the penetration test, using clear and concise language. Deliver a comprehensive report detailing all vulnerabilities discovered, the methods used to exploit them, and the potential impact. Include actionable recommendations for remediation, prioritizing the most critical vulnerabilities.

We have a Tech Effect episode dedicated to cybersecurity testing and how to keep safe from hackers. Check it out below:

Penetration testing—Key takeaways

Penetration testing is essential for safeguarding an organization's digital assets, especially now when cyberattacks are increasingly sophisticated and frequent. Regular penetration testing helps organizations stay one step ahead of potential threats. It provides actionable insights that are critical for strengthening defenses, mitigating risks, and fostering a security-aware culture within the organization.

Don’t wait for a breach to test your defenses. Make penetration testing a regular part of your security routine to identify vulnerabilities before they can be exploited. We can help you with everything you need to get started. Contact us to learn more about our security and penetration testing services.