Penetration tests are controlled cyberattack simulations designed to evaluate your organization’s security posture. By testing against real-world attack tactics, pentests uncover vulnerabilities in your systems and help you understand how to strengthen your defenses. They are also a critical component of cybersecurity compliance frameworks like NIST CSF, PCI-DSS, and FedRAMP. 

How to conduct penetration tests

Organizations that want to uncover vulnerabilities in their IT infrastructure have multiple penetration testing methodologies to choose from. Depending on the specific objectives for the testing exercise, these methods may be applied individually or combined together: 

• External testing focuses on assessing the security of an enterprise's public-facing IT assets, such as web applications, email systems, and self-service applications. The process often involves simulating phishing attacks and leveraging other initial access tactics to exploit these external-facing components. This approach helps identify weaknesses that cybercriminals could exploit without prior access to internal systems. 

• Internal testing is conducted from within the network, simulating a scenario where an attacker has already bypassed external defenses. This could involve stolen employee credentials or unauthorized access by an insider. By replicating the actions of a malicious insider or rogue employee, this test highlights potential vulnerabilities associated with insider threats and credential-based attacks. 

• Blind testing involves attempting to breach the enterprise network using brute force or other methods without any prior knowledge of the system. This approach simulates a real-world attack by an external threat actor, providing valuable insights into how security measures hold up under an unplanned assault and how attackers adapt during the process. 

• Double-blind testing takes the blind test one step further. Neither the penetration tester nor the organization's security team has prior knowledge of when the attack will occur or what techniques will be used. This realistically simulates an unpredictable attack scenario, requiring the incident response team to adapt their approach as the attack unfolds. 

• Targeted testing involves close collaboration between the penetration tester and the organization's security team. Both parties are aware of the test details, making this method less about uncovering hidden vulnerabilities and more about training and preparation. Security teams use this approach to familiarize themselves with emerging attack methodologies and better understand the behaviors and tactics of cybercriminals. 

Each of these methods plays a critical role in identifying and mitigating security risks, ensuring an organization's defenses remain robust against evolving threats. 

Penetration testing vs. vulnerability management

It’s easy to confuse penetration testing with vulnerability management, but they serve different purposes: 

• Vulnerability management identifies security flaws and provides recommendations for remediation. Once a vulnerability is patched, a follow-up scan confirms the issue is resolved. 

• Penetration testing goes a step further by exploiting vulnerabilities to demonstrate the potential impact of an actual breach. This provides deeper insights into the severity of risks. 

While penetration tests often include vulnerability scans, vulnerability management doesn’t typically involve active exploitation of those vulnerabilities. Both processes typically focus on technical vulnerabilities within IT systems. Sometimes phishing and social engineering attacks are included in specialized tests, but these are not standard for most compliance-driven pentesting exercises.  

Who performs penetration testing?

Penetration testers are also known as ethical hackers. These professionals combine technical expertise with real-world attack knowledge to identify vulnerabilities without harming your systems. They document their findings in detailed reports, showing exactly how they exploited vulnerabilities and the potential damage that could occur in a real attack. 

Three categories of penetration tests explained

Penetration testing exercises fall into one of three broad categories: 

1. White box testing. Testers have full visibility into your network and systems, including source code. This method is ideal for automated testing and frequent assessments of development environments, as it ensures no vulnerabilities are overlooked. 

1. Black box testing. Testers start with no prior knowledge of your systems. This approach mirrors the perspective of an external attacker and requires manual expertise to uncover vulnerabilities. Black box testing provides a comprehensive view of your organization’s ability to defend against external threats. 

1. Grey box testing. Testers receive limited information about your systems, such as user credentials or network architecture. This type of test focuses on scenarios where a trusted insider could escalate privileges or collaborate with external attackers to breach security. 

The stages of penetration testing

Penetration tests follow a structured process to simulate real-world attacks: 

1. Reconnaissance: Testers gather information on open ports and exposed assets using tools like Nmap and Wireshark. 
2. Scanning: Vulnerability scanning tools like Metasploit identify known and zero-day vulnerabilities, allowing penetration testers to develop an attack strategy. 
3. Exploitation: Testers exploit vulnerabilities to assess their impact, often using the same tools and techniques employed by real-world threat actors. 
4. Backdoor installation: To simulate a persistent threat, testers may create hidden mechanisms to gain access to systems without authenticating. 
5. Anti-tracking: Testers may evaluate detection capabilities using techniques to obscure their activities, mimicking the way attackers evade detection when conducting attacks. 

The results of these stages are documented in detail, offering actionable insights to improve your security posture. 

What to do after a successful penetration testing exercise

After completing a penetration test, the ethical hacker will share a comprehensive report with your security team. This report outlines the vulnerabilities discovered, how they were exploited, and the potential impact of each issue. The next step is to use these findings to strengthen your defenses and address any weaknesses. 

For web applications, this might involve implementing rate limiting, updating Web Application Firewall (WAF) rules, and adding DDoS mitigation measures. Additional actions could include tightening form validations and improving input sanitization to prevent injection attacks. 

For internal networks, recommended upgrades might include deploying a secure web gateway, adopting a Zero Trust security model, or enhancing network segmentation. If the test revealed weak security policies or poor policy enforcement, the organization might provide employees with security awareness training and reevaluate access control policies to minimize lateral movement risks. 

It’s also important to prioritize and track remediation efforts to ensure vulnerabilities are effectively addressed. Regular follow-up tests can confirm that the fixes are working as intended and ensure new vulnerabilities haven’t emerged in the meantime.