Penetration Testing

What is penetration testing?

A pen test, or penetration test, is more than just a cybersecurity drill—it’s a proactive strategy to uncover vulnerabilities before malicious actors do. By simulating real-world attacks, pen tests expose weaknesses in your systems, processes, and even personnel. These insights empower your organization to strengthen defenses and mitigate risks before they escalate into breaches.

Penetration testing isn’t just about technical resilience; it’s a compliance ally. Regulations like PCI DSS, HIPAA, and GDPR mandate rigorous testing to protect sensitive data. Beyond meeting these requirements, pen tests provide peace of mind to stakeholders and demonstrate your commitment to safeguarding valuable information.

Whether you’re addressing a new system rollout, evaluating changes to infrastructure, or validating an existing security posture, pen testing is an essential step toward proactive cybersecurity.

Why penetration testing matters

Cybersecurity is a dynamic challenge, with attackers growing more sophisticated every day. Penetration testing bridges the gap between what you assume about your defenses and what’s truly secure. Here’s why it’s a non-negotiable element of modern security:

1. Spot hidden vulnerabilities

Every IT environment has blind spots. Whether it’s misconfigured systems, overlooked patches, or insecure APIs, pen testing uncovers these issues before they’re exploited.

2. Strengthen defenses

By simulating real-world tactics—like phishing, SQL injections, or brute-force attacks—pen tests expose how an attacker might compromise your environment. This real-time insight enables organizations to fine-tune their defenses.

3. Ensure compliance

Compliance frameworks such as ISO/IEC 27001 and GDPR don’t just recommend pen testing; they rely on it to validate that your controls are functioning as intended. Pen tests help you meet these stringent requirements and avoid costly fines.

4. Build executive buy-in

Pen test results aren’t just technical reports—they’re actionable insights that can drive security investments. A well-documented test provides clarity for decision-makers, making it easier to prioritize resources effectively.

By identifying vulnerabilities, pen tests save organizations from reactive spending and the reputational damage of data breaches.

Types of penetration testing

No two systems are alike, and pen testing adapts to meet diverse security needs. Different tests focus on varying environments, ensuring comprehensive protection across your digital footprint.

Internal pen testing

This test evaluates threats originating from inside the organization, such as disgruntled employees or compromised accounts. Internal pen tests reveal gaps in access control and monitoring processes.

External pen testing

Focused on internet-facing assets like websites, servers, or firewalls, external pen tests simulate what an attacker would do without internal privileges.

Web application testing

With web apps being prime targets, this type identifies vulnerabilities in source code, databases, and backend systems. Issues like cross-site scripting (XSS) and injection attacks are common discoveries.

Social engineering

Testing Human error remains a leading cause of breaches. These tests evaluate your team’s resilience to phishing emails, pretext calls, or physical impersonation attempts.

Mobile and IoT testing

Connected devices bring convenience—and risk. Pen testing these environments helps secure mobile applications, smart devices, and IoT ecosystems.

Cloud and API testing

Cloud configurations and APIs are pivotal to modern systems. Testing ensures these elements are secure against threats like unauthorized access, privilege escalation, or data leakage.

Specialized tests

From embedded devices like IoT to CI/CD pipelines critical for DevOps environments, specialized tests cater to unique challenges in your infrastructure. Each type of testing targets a specific layer of your system, ensuring no vulnerability goes unchecked.

The penetration testing process

Penetration testing is a structured and systematic process designed to uncover vulnerabilities in your environment. Each phase builds on the last, ensuring a thorough evaluation of your systems, networks, and applications. Here’s an in-depth look at each step:

1. Reconnaissance phase

The reconnaissance phase, often called the "information-gathering" stage, is where pen testers learn as much as possible about their target before launching an attack simulation.

Key activities:

• Passive reconnaissance: Collecting information from publicly available sources, such as websites, DNS records, social media, and forums. Tools like Maltego or Recon-ng help map relationships and potential vulnerabilities.
• Active reconnaissance: Probing systems directly using port scans, ping sweeps, and other methods to identify active hosts, services, and potential entry points.

Purpose: This phase mirrors the behavior of real-world attackers, who often spend significant time mapping out their target to find weaknesses. A detailed reconnaissance phase ensures the pen test is targeted and efficient.

2. Scanning

Once information has been gathered, pen testers move on to scanning. This step is about actively identifying vulnerabilities, misconfigurations, and exploitable gaps in systems or applications.

Key techniques:

• Network scanning: Identifying active systems, open ports, and services using tools like Nmap or Masscan.
• Vulnerability scanning: Automated tools such as Nessus or OpenVAS identify weaknesses like outdated software, missing patches, or misconfigurations.
• Application scanning: Tools like Burp Suite or OWASP ZAP examine web applications for issues like SQL injection, cross-site scripting (XSS), and insecure APIs.

Purpose: This step helps testers prioritize targets by highlighting systems or applications with the most significant vulnerabilities. It’s a foundational step that informs the attack strategy.

3. Gaining access

The gaining access phase is where the real action begins. Testers leverage the vulnerabilities identified during scanning to penetrate the system and gain unauthorized access.

Key techniques:

• Exploitation: Tools like Metasploit Framework allow testers to execute specific exploits, such as buffer overflows or privilege escalation attacks.
• Social engineering: Phishing emails, pretexting, or baiting tactics test whether employees are susceptible to manipulation.
• Credential attacks: Brute-forcing passwords using tools like Hydra or Hashcat to assess the strength of authentication systems.

Purpose: This phase reveals how vulnerabilities can be exploited and the level of access an attacker could gain. It also demonstrates potential damage, such as accessing sensitive data or critical systems.

4. Maintaining access

Maintaining access, often referred to as the post-exploitation phase, evaluates how attackers could remain in your systems without detection. Advanced Persistent Threats (APTs) often operate in this phase, leveraging persistence techniques to continue their attack over time.

Key techniques:

• Backdoors and rootkits: Installing tools or scripts to enable attackers to return later without re-exploiting vulnerabilities.
• Privilege escalation: Gaining higher levels of access within the system to control more critical assets.
• Lateral movement: Moving between systems, such as from a workstation to a server, to broaden the scope of the attack.

Purpose: This phase demonstrates the potential long-term impact of a breach, showing how attackers could exploit their foothold to gain deeper access or exfiltrate sensitive data.

5. Covering tracks and reporting

The final phase of a pen test is twofold: ensuring no trace of the test remains on the systems and delivering a comprehensive report of findings.

Key activities:

• Removing artifacts: Testers clean up any files, logs, or traces of their activity to restore the system to its original state.
• Documenting findings: A detailed report includes:

Vulnerabilities discovered.
Exploitation techniques used.
The potential business impact of each vulnerability.
Recommendations for remediation and future improvements.

Purpose: The reporting phase ensures that the organization understands its vulnerabilities and has a clear path to address them. It also provides documentation for stakeholders, regulators, and auditors.

Why the penetration testing process matters

Every step of the penetration testing process is critical to achieving actionable results. A thorough process ensures that no vulnerability is missed, providing a comprehensive evaluation of your security posture. Additionally, following a structured methodology builds trust and ensures that the test aligns with industry standards and best practices.

Penetration testing isn’t just about finding weaknesses; it’s about empowering organizations to proactively secure their systems and confidently face evolving threats.

When should you conduct a pen test?

The timing of a pen test can make or break its impact. Organizations should consider the following:

• During system development: Conduct tests during early development stages to prevent vulnerabilities from being built into production systems.
• After significant changes: Infrastructure updates, new software integrations, or process overhauls often introduce unintentional weaknesses.
• Regular intervals: Cyber threats evolve, and so should your defenses. Annual or quarterly pen tests keep your security aligned with current risks.

Proactive testing ensures your defenses remain strong even as your environment changes.

Who conducts pen tests?

Pen tests demand expertise, precision, and trust. Certified penetration testers—often ethical hackers—are skilled professionals trained to think like attackers.

These individuals bring experience in simulating real-world threats while adhering to ethical and legal standards. Certifications like CREST, Offensive Security Certified Professional (OSCP), and NCSC ensure their methods meet industry benchmarks.

Tools of the trade

Penetration testers rely on a diverse toolkit to uncover vulnerabilities, simulate real-world attacks, and evaluate the resilience of your systems. These tools range from reconnaissance and scanning utilities to exploitation and post-exploitation frameworks.

Here’s a closer look at the categories and how they’re used:

1. Reconnaissance tools

The first step of any pen test is gathering intelligence. Reconnaissance tools help testers map your attack surface and identify potential entry points.

• Port scanners: Tools like Nmap or Masscan identify open ports and services running on systems, revealing potential vulnerabilities.
• Network mapping tools: Tools such as Maltego visualize network structures and relationships, aiding testers in understanding the organization’s infrastructure.
• DNS recon tools: Utilities like Recon-ng or Sublist3r discover subdomains and DNS records, exposing assets that may be unintentionally public.

These tools help testers understand your environment as an attacker would, enabling precise targeting.

2. Vulnerability scanners

Automated vulnerability scanners are essential for identifying weaknesses in networks, applications, and APIs.

• Nessus: A popular scanner for identifying misconfigurations, outdated software, and known vulnerabilities.
• OpenVAS: An open-source alternative that provides extensive vulnerability checks across various platforms.
• Nikto: Focuses on identifying security issues in web servers and applications, such as outdated server software or insecure headers.

Vulnerability scanners provide a foundation for the next phase of the test by highlighting areas of concern.

3. Proxy tools

Proxy tools are indispensable for analyzing and intercepting network traffic.

• Burp Suite: Widely used for web application security testing, this tool allows testers to manipulate HTTP/S requests, uncover authentication flaws, or identify insecure APIs.
• OWASP ZAP (Zed Attack Proxy): An open-source proxy tool ideal for identifying common vulnerabilities like cross-site scripting (XSS) or SQL injection.

By intercepting and modifying traffic between clients and servers, proxy tools reveal vulnerabilities in real-time data exchanges.

4. Exploitation tools

Exploitation tools are used to simulate attacks on identified vulnerabilities, assessing their impact and potential damage.

• Metasploit Framework: A versatile tool that allows testers to exploit weaknesses, test payloads, and simulate advanced attacks.
• Sqlmap: Automates the detection and exploitation of SQL injection vulnerabilities, a common attack vector for web applications.
• Hydra: A powerful tool for brute-force attacks, used to test the strength of authentication systems like passwords or PINs.

These tools let testers move from identification to action, showing what an attacker could achieve if the vulnerability were exploited.

5. Post-exploitation tools

Once access is gained, post-exploitation tools evaluate how attackers could maintain control, pivot within the system, or extract valuable data.

• Cobalt Strike: Simulates advanced persistent threats (APTs) and helps testers understand how attackers could maintain a foothold in the network.
• Empire: A post-exploitation framework for stealthy lateral movement, privilege escalation, and data exfiltration.
• BloodHound: Maps Active Directory environments to identify potential paths for privilege escalation or domain-wide compromise.

These tools help demonstrate the full potential impact of a breach, emphasizing the importance of proactive mitigation.

6. Specialized operating systems

Many pen testers use purpose-built operating systems loaded with a wide array of tools for all phases of testing.

• Kali Linux: The most popular OS for penetration testing, offering over 600 pre-installed security tools.
• Parrot Security OS: A lightweight alternative to Kali Linux, ideal for resource-constrained environments.
• BlackArch Linux: A comprehensive security OS for advanced testers, offering thousands of tools.

These operating systems streamline the testing process by providing ready-to-use tools in a single environment.

7. Credential testing tools

Credential testing tools evaluate the strength of authentication mechanisms, including passwords, API keys, and SSH credentials.

• John the Ripper: A popular password-cracking tool that works on encrypted files, hashes, and authentication systems.
• Hashcat: Known for its speed, this tool cracks complex password hashes using GPU acceleration.
• Medusa: Focuses on brute-forcing authentication for remote services like FTP, HTTP, or Telnet.

These tools test whether weak credentials could provide attackers with unauthorized access to systems.

8. Reporting tools

The final stage of any pen test is delivering actionable insights. Reporting tools help testers compile findings, document vulnerabilities, and recommend remediation steps.

• Dradis: A collaborative platform that consolidates test results from multiple tools into a unified report.
• Faraday: An IDE-like environment for security assessments, enabling team collaboration and efficient reporting.
• Metasploit Pro: Combines testing and reporting, offering detailed vulnerability insights and risk assessments.

The value of a comprehensive toolset

Each tool plays a distinct role in the penetration testing lifecycle, from reconnaissance to remediation. When used effectively, these tools uncover not only technical vulnerabilities but also highlight areas for process improvement and staff training.

A penetration tester’s ability to adapt these tools to the specific environment they’re testing makes the difference between identifying surface-level issues and uncovering critical risks.

What happens after a pen test?

The value of a penetration test isn’t just in the vulnerabilities it uncovers—it’s in how those insights are used to strengthen your organization’s security posture. A pen test is a launching point for meaningful action, ensuring that identified weaknesses are addressed and future threats mitigated.

Here’s what comes next:

1. Review results in detail

After the test, penetration testers provide a detailed report that outlines:

1. Vulnerabilities discovered during the test.
2. The methods used to exploit these vulnerabilities.
3. The potential impact of each vulnerability if left unaddressed.
4. A prioritized list of recommended remediation steps. These findings provide a clear roadmap for action, ensuring your resources are directed where they’re needed most.

2. Develop a comprehensive remediation plan

Collaboration is key at this stage. Your IT and security teams work together to implement the fixes recommended in the report. These can range from patching software and reconfiguring systems to updating policies or improving employee training.

3. Strengthen organizational awareness

A penetration test often reveals weaknesses in employee awareness, such as susceptibility to phishing attacks. Use the findings to conduct targeted training sessions, improving your team’s ability to recognize and respond to threats.

4. Retest and validate

Once fixes are implemented, follow-up testing is critical. This ensures that vulnerabilities are fully resolved and that no new issues have been introduced in the process. Regular scans and periodic pen tests should become part of your security routine.

5. Document and share findings with stakeholders

Transparency is essential for building trust. Use the test results to communicate with stakeholders, demonstrating your commitment to maintaining robust cybersecurity measures.

The aftermath of a pen test isn’t the end of the story—it’s the beginning of a proactive, evolving security strategy.

The role of teaming

Penetration testing reaches its full potential when paired with effective teaming exercises. These exercises bridge the gap between offense and defense, fostering collaboration and driving continuous improvement in your security approach.

Red Teams
Red teams operate as ethical adversaries. Their role is to think like attackers, identifying weaknesses in your defenses and exploiting them to demonstrate their potential impact. This isn’t about blame—it’s about finding gaps you might otherwise overlook.

Blue Teams
Blue teams are your defensive line. They focus on detecting, responding to, and mitigating threats in real time. By testing their capabilities against simulated attacks from the red team, they can identify areas for improvement and refine their processes.

Purple Teams
The purple team is where the magic happens. Acting as a bridge between red and blue teams, their purpose is to facilitate knowledge sharing and foster collaboration. By blending offensive and defensive insights, purple teams enable both sides to learn from each other, creating a more resilient security posture.

Why teaming matters

Teaming exercises aren’t just hypothetical—they simulate real-world scenarios that test your organization’s ability to adapt and respond to threats. They also:

• Promote a culture of continuous learning and improvement.
• Highlight weaknesses in communication or coordination during incidents.
• Drive innovation by encouraging creative problem-solving from both sides.

By integrating teaming exercises into your security strategy, you can transform pen testing from a one-time assessment into an ongoing cycle of improvement.

Compliance through pen testing

Compliance isn’t optional. Regulations like PCI DSS, HIPAA, GDPR, and ISO/IEC 27001 require organizations to validate the effectiveness of their security controls—and penetration testing is one of the most effective ways to do so.

How pen testing supports compliance

Validates security controls: Compliance standards often require organizations to test and document the effectiveness of their defenses. A penetration test demonstrates that your controls work as intended, providing tangible proof of compliance.

Addresses audit requirements: Many frameworks mandate regular testing and reporting. Penetration test reports serve as comprehensive documentation that auditors can review to verify compliance efforts.

Strengthens incident response: Readiness Pen tests highlight potential attack vectors, helping you prepare for real incidents. This aligns with regulatory requirements that emphasize proactive risk management and incident response planning.

Going beyond the checklist

While compliance is a critical driver for pen testing, it’s not the end goal. True security requires looking beyond regulatory requirements and treating pen tests as an opportunity to improve resilience, rather than a box to tick.

Compliance through pen testing isn’t just about avoiding fines—it’s about demonstrating your commitment to protecting sensitive data and building trust with your stakeholders.

Related information: Streamlining compliance: The power of broad cybersecurity frameworks

How does pen testing differ from automated testing?

Pen testing and automated testing both play essential roles in cybersecurity, but they serve different purposes and offer unique benefits. Understanding these differences helps you leverage both approaches effectively.

Manual pen testing: depth and insight

Manual penetration testing is the gold standard for uncovering complex vulnerabilities. Skilled testers think like attackers, using creativity and experience to simulate real-world scenarios that automated tools often miss.

What it excels at:

• Identifying business logic flaws (e.g., improper permissions or application misuse).
• Mimicking advanced persistent threats that require lateral movement across networks.
• Evaluating the human element, such as susceptibility to phishing or social engineering.

Challenges:

Manual pen testing is labor-intensive and requires highly skilled professionals, which can make it more expensive and time-consuming.

Automated testing: speed and consistency

Automated tools use predefined scripts to scan for known vulnerabilities. These tests are quick, scalable, and ideal for routine assessments.

What it excels at:

• Scanning large environments for common misconfigurations or outdated systems.
• Delivering consistent results across repeated tests.
• Integrating into DevSecOps pipelines for continuous security validation.

Challenges:

While efficient, automated testing lacks the adaptability of human testers. It’s prone to false positives and often overlooks nuanced vulnerabilities.

The power of combining both

Penetration testing and automated testing aren’t mutually exclusive—they’re complementary. By integrating both approaches, you can:

• Gain comprehensive coverage, addressing both basic vulnerabilities and complex risks.
• Use automated tools for routine scans and rely on pen testers for high-risk areas.
• Create a layered defense strategy that evolves with your security needs.

Manual pen testing provides depth, while automated testing delivers breadth. Together, they form a complete picture of your organization’s security landscape.

Penetration testing isn’t just about identifying vulnerabilities—it’s about empowering your organization to act proactively, build resilience, and stay ahead of evolving threats. From compliance validation to strengthening defenses, a thorough pen test is an investment in trust, security, and business continuity.

More Pen  Testing Resources:

Podcasts

Penetration Testing Top Tips with Dave Kennedy
Privilege Escalation with Carlos Polop