Penetration Testing: When, Why, and How to Do It Right

Introduction

I am reluctant to frame penetration testing as a starting point for your product security program, as there are many other proactive security investments that should come first. However, you may find yourself needing a third-party penetration test due to compliance requirements or client demands. Whether you're new to penetration testing or looking to refine your approach, let's explore what it entails and how to run an effective program.

The Role of Penetration Testing in a Security Program

Penetration testing, or pen testing, is a controlled, simulated cyberattack used to evaluate security of an organization's systems, applications, and networks. It plays a crucial role in a mature security program by identifying vulnerabilities before they can be exploited by malicious actors. However, penetration testing can provide value even if an organization does not have a fully mature security program. It serves as a baseline assessment and can help organizations build a roadmap for improving their security posture over time. When properly integrated, pen testing also validates the ongoing success of a security program.

When Should You Conduct a Pen Test?

The timing of penetration testing depends on multiple factors, including compliance requirements, software release cycles, and the organization's risk tolerance. Some best practices include:

• Regular Testing Cadence: Conducting tests annually or quarterly ensures continued security coverage.
• Before Major Releases: Testing before launching a new product or feature helps catch vulnerabilities before they reach customers.
• After Significant Changes: Infrastructure changes, mergers, or cloud migrations introduce new risks that should be evaluated.
• Compliance and Audit Requirements: Many regulatory frameworks, such as PCI-DSS and SOC 2, require periodic penetration testing.

Preparing for a Penetration Test

Proper preparation ensures the test is as effective as possible. Key considerations include:

• Deciding Which Environment to Test: Whether to test in production, staging, or a separate security testing environment. Testing in production is risky by the very nature of what testers will do—it can cause outages, trigger security alerts, or even disrupt customer operations. However, it provides the most realistic assessment of real-world attack scenarios. Staging environments reduce risk but may lack full parity with production, which can lead to missed vulnerabilities, and frequent testing there can slow down development velocity. Setting up a dedicated security testing environment offers control and minimizes disruption, but it adds cost and requires ongoing maintenance to remain useful. Organizations should weigh these trade-offs carefully when determining their approach.

• Informing Operational Teams: Ensuring Site Reliability Engineering (SRE) and Security Operations Center (SOC) teams are aware to prevent false alarms that could halt valuable (and expensive) testing. Proper coordination allows security teams to differentiate between legitimate penetration testing activities and actual threat actors, which is crucial if a real attack occurs during an engagement. Establishing clear communication and logging mechanisms ensures that security teams can monitor the test without unnecessary disruptions while still being prepared to respond to genuine threats.
• IP Address Handling: Determining whether to allowlist (whitelist) the tester's IP range and corresponding WAF rules to prevent unnecessary blocking. Keeping the WAF active during testing helps establish whether security controls are functioning correctly, while temporarily disabling the WAF can allow testers to uncover deeper vulnerabilities that might be masked by automated protections—useful for understanding the security posture if the WAF were to fail.
• Training Testers on the System: Providing training, interaction with product and support teams, and allowing time for testers to understand the application's architecture and threat model. While testers don’t necessarily need full access to everything, providing an architectural overview is beneficial. Ensuring they have at least the same level of product knowledge as a typical customer helps them better understand how the system is used in real-world scenarios, ultimately leading to more effective testing.
• Provisioning Access: Ensuring testers have appropriate credentials for different application roles (user, administrator, etc.), as well as access to the codebase, relevant documentation (such as user and API documents), VPN access if required, and other necessary IT resources. These tasks take time, and it is crucial to complete them before the engagement begins to ensure the pen testing team can maximize their time identifying vulnerabilities rather than waiting for access.
• Agreeing on Test Scope: Clearly defining which systems, applications, and test cases are in-scope versus out-of-scope. Beware of security teams rejecting findings by claiming they are "out of scope"—vulnerabilities don’t disappear just because they weren’t included in the official scope. Ignoring security issues is not an effective risk management strategy.

White-Box vs. Black-Box Testing

One of the key decisions in penetration testing is whether to conduct a white-box or black-box test.

White-Box Testing

White-box testing provides testers with full access to the application’s source code, architecture, and design documents.

Pros:

• More thorough testing, as security researchers can target the weakest parts of the codebase.
• Faster identification of vulnerabilities, reducing overall testing time.
• Fewer false positives, as findings are based on deep system knowledge.

Cons:

• Requires granting significant access, which necessitates strict NDAs and confidentiality agreements.
• Can be more expensive and time-consuming to ramp up a testing team.

Black-Box Testing

Black-box testing simulates an external attack without prior knowledge of the system’s internals.

Pros:

• Provides a realistic assessment of how an external attacker would approach the system.
• Tests security controls such as authentication, access control, and rate limiting.

Cons:

• May miss vulnerabilities that require deep code analysis.
• Requires extensive reconnaissance and trial-and-error probing, leading to longer engagements.

For most organizations, a hybrid approach—granting testers enough internal knowledge to focus their efforts while still simulating real-world attack scenarios—is ideal.

Web, Mobile, and API Penetration Testing Differences

Different application types require different testing methodologies:

• Web Applications: Typically involve testing for vulnerabilities like SQL injection, cross-site scripting (XSS), and authentication bypasses.
• Mobile Applications: Require testing on both client-side and backend API interactions, with additional considerations for data storage and reverse engineering threats.
• API Endpoints: Focus on authentication flaws, data exposure, and improper access controls, ensuring APIs are secure against unauthorized access and data leaks.

Choosing the Right Penetration Testing Vendor

Selecting a penetration testing vendor is a critical decision. Common pitfalls include:

• Over-reliance on Automated Scans: A quality pen test should include manual testing, as automated tools alone often miss business logic vulnerabilities.
• Lack of Application Familiarity: A vendor that does not take the time to understand your application’s architecture will provide a lower-quality test.
• Superficial Reports: A report with no major findings is a red flag—every system has vulnerabilities, and a quality test should uncover meaningful areas for improvement.

There are advantages and disadvantages to working with both large penetration testing firms and boutique security firms. Large firms bring scale, brand recognition, and a broad range of services, while boutique firms often provide deeper engagement, more tailored findings, and greater flexibility. Cost, scale, and capability should all be considered when selecting a vendor.

Organizations should ensure:

• NDAs and Confidentiality Agreements: Protecting sensitive information shared during testing.
• Clear Contracts and Pricing Agreements: Establishing expectations for scope, methodology, and deliverables.
• Periodic Vendor Rotation: Using the same vendor repeatedly can lead to regulatory capture, where complacency results in overlooked vulnerabilities. Engaging different vendors periodically helps maintain fresh perspectives and more rigorous testing—this isn’t about mistrust, but about ensuring fresh perspectives and thorough testing over time..

Handling Pen Test Findings: Reporting and Remediation

The objective of penetration testing is to find real security issues that need to be addressed. A report that claims no findings is a red flag—either the testing was insufficient, or the findings were omitted. Every system has vulnerabilities, and meaningful testing should uncover actionable insights that help improve security. That said, not all findings are equally critical, which is why prioritization is key.

Once a penetration test is complete, handling the results correctly is crucial. Remediation starts with risk mapping and prioritization, ensuring that critical vulnerabilities are addressed first. We previously covered risk management and prioritization strategies, which should be applied when interpreting pen test results. The findings should be divided into two primary reports:

1. Technical Report: A comprehensive, detailed breakdown of vulnerabilities for the security and engineering teams. This should include:
2. Executive Report: A high-level summary for leadership and external stakeholders, such as customers and auditors. Transparency in penetration testing results is increasingly expected in SaaS sales and customer relationships. Prospects and customers often require visibility into security testing efforts and remediation plans to assess risk. Having a structured program with a strong history of executive reports and completed remediation plans can replace customer-initiated penetration testing requirements, reducing cost and minimizing operational disruptions. This report should include:

Conclusion

Penetration testing is a critical component of a robust security program, but its effectiveness depends on timing, methodology, vendor selection, and how findings are handled. A well-structured penetration testing program goes beyond compliance checkboxes—it provides actionable insights that strengthen an organization's security posture and reduce risk.

By taking a strategic approach—choosing the right mix of white-box and black-box testing, involving key stakeholders, ensuring actionable reporting, properly preparing for the test, and periodically rotating vendors—you can maximize the value of penetration testing and maintain a proactive security stance.

Security is an ongoing journey, and penetration testing is one of many essential tools in your arsenal. Start evaluating your current penetration testing strategy today—ensure you're engaging the right vendors, prioritizing meaningful findings, and integrating results into a continuous security improvement process.

How do you handle penetration testing today? Have you encountered any challenges in vendor selection, reporting, or remediation that others might learn from? Please share your insights!