Penetration testing (pen testing) is an essential aspect of cybersecurity. It simulates cyberattacks to identify vulnerabilities within systems, networks, or applications before malicious hackers exploit them. However, even seasoned professionals can make mistakes during penetration testing. These errors can lead to incomplete assessments, misreporting, and, in some cases, unintended damage to the target system.

In this article, we will explore the most common mistakes made during penetration tests and provide actionable steps on how to avoid them. From inadequate scoping to missing crucial vulnerabilities, understanding these pitfalls can significantly improve the quality and success of penetration testing engagements.

1. Inadequate Scoping and Planning

Mistake: One of the most common mistakes during penetration testing is failing to adequately scope and plan the engagement. Without a clear understanding of the target, the objectives, and the boundaries of the test, the test may result in wasted effort, unnecessary risk, or missed vulnerabilities.

How to Avoid It:

• Define the Scope: A clear scope defines what is included in the test, such as specific systems, applications, or networks. It also outlines what is excluded, to avoid overstepping boundaries or violating regulations.
• Obtain Permission: Always ensure written authorization from stakeholders before starting the test. This protects both the testers and the organization from legal issues.
• Set Expectations: Understand the business goals of the test, whether it’s identifying vulnerabilities, testing incident response, or assessing compliance with security standards.

Example: Suppose a penetration test is being performed on a company's internal network, but the scope isn't clear about which systems are in-scope or out-of-scope. The tester may unintentionally cause disruptions or miss crucial systems that are part of the security risk.

2. Ignoring the Rules of Engagement

Mistake: The "Rules of Engagement" (RoE) are a critical part of any penetration test. Ignoring or not clearly defining these rules can lead to mistakes that could harm the target system or cause disruptions. These rules should define testing hours, levels of aggression, and the boundaries of the attack.

How to Avoid It:

• Create Clear Rules: Ensure that both the testing team and the target organization agree on a set of clear rules. This includes things like the time window for testing, whether denial-of-service attacks are allowed, and what types of exploits can be used.
• Coordinate with Stakeholders: Always inform key stakeholders (e.g., IT, system administrators) about the testing activities and make sure they understand that no critical systems will be harmed during testing.

Example: A tester might use an aggressive denial-of-service (DoS) attack during a penetration test without confirming if this is within the agreed-upon rules. This could bring down the company’s production servers, causing an unintended loss of service.

3. Failing to Perform a Comprehensive Reconnaissance Phase

Mistake: Reconnaissance, or “recon,” is a critical first step in any penetration test. Skipping this phase or performing it insufficiently can lead to missed vulnerabilities or misdirected attacks. Many testers focus on active scanning and exploitation without gathering enough passive intelligence first.

How to Avoid It:

• Thorough Passive Recon: Before actively engaging with a target system, focus on gathering as much passive intelligence as possible. This includes examining DNS records, IP ranges, WHOIS data, and other publicly available information.
• Active Recon: Perform active reconnaissance through network scanning, enumeration, and banner grabbing. This will help you map out the target's infrastructure, detect potential weak points, and understand the systems you're dealing with.
• Identify and List All Attack Surfaces: Recon helps identify attack surfaces like open ports, running services, and outdated software versions.

Example: A penetration tester might miss a crucial vulnerability in a web server because they didn’t first perform an adequate scan to identify outdated versions or misconfigurations in the services running on the system.

4. Overlooking the Importance of Post-Exploitation

Mistake: Once an attacker has successfully exploited a system, the focus should shift to post-exploitation activities. A common mistake is either neglecting this phase or not providing enough depth to it. Post-exploitation is crucial for identifying sensitive data and lateral movement opportunities within the network.

How to Avoid It:

• Focus on Persistence and Lateral Movement: After gaining access to a system, test if the attacker can maintain access, escalate privileges, or move laterally across the network. This highlights deeper vulnerabilities that may be more difficult to patch.
• Look for Sensitive Data: Check for sensitive data (e.g., password files, configuration files) that could be exfiltrated or abused if exploited by an attacker.
• Document Findings: Carefully document each post-exploitation activity to provide actionable insights to the client. This information helps in mitigating risks and fortifying the network.

Example: After exploiting a system, the tester might not investigate if they can escalate privileges or exfiltrate sensitive customer data, which could have been an important aspect of the assessment.

5. Over-Reliance on Automated Tools

Mistake: Automated tools can be highly effective for scanning large networks and systems, but they shouldn’t be relied upon exclusively. Many pen testers make the mistake of trusting automated scanners without validating their results or performing manual testing.

How to Avoid It:

• Manual Verification: Always verify automated tool results manually. False positives and missed vulnerabilities are common when relying solely on automation. Manual testing can also uncover complex vulnerabilities that automated tools might overlook.
• Use Tools as a Guide: Automated tools should be used to guide the tester to areas that need further exploration. Always complement automated findings with human analysis and creativity.

Example: A vulnerability scanner may flag an open port as a critical risk, but a manual inspection may reveal that it’s a secure service that’s properly configured. Relying solely on the automated tool could lead to unnecessary alarm or missed attack vectors.

6. Not Considering the Impact on Business Operations

Mistake: Penetration testing can be intrusive, especially when performing active exploitation or stress testing. Failing to account for the potential impact on business operations is a serious mistake. If the test brings down critical systems, it could disrupt operations or harm the organization financially.

How to Avoid It:

• Perform Tests During Off-Hours: Schedule penetration tests during off-peak hours when the risk to business operations is minimal. Work with the client to choose the most appropriate timing.
• Impact Assessment: Understand the potential impact of each test on business systems. If there is any doubt about the possible effect, ask for permission to proceed.
• Simulate Real-World Attacks: Penetration tests should simulate real-world attacks but should be done carefully to minimize disruptions. This can include simulating a data breach or a DDoS attack without compromising critical services.

Example: A tester may attempt to exploit a vulnerability during the day on a live system, leading to a service outage for the organization’s customers. This could result in financial loss and a damaged reputation.

7. Failure to Communicate Findings Effectively

Mistake: Another common mistake is failing to communicate the findings of a penetration test effectively. The success of a penetration test depends on how well the results are presented to stakeholders. If vulnerabilities are not clearly explained, the organization may fail to address them adequately.

How to Avoid It:

• Clear and Actionable Reporting: Provide clear, actionable reports that include risk ratings, detailed descriptions of vulnerabilities, and recommended remediation steps.
• Executive Summaries: Tailor reports to different audiences. Provide executive summaries for non-technical stakeholders, while more technical details should be shared with the IT team responsible for patching the vulnerabilities.
• Proof of Concept: Include proof of concept (PoC) for exploits to help the client understand how an attacker could take advantage of the vulnerability.

Example: A penetration tester discovers an SQL injection vulnerability but doesn’t provide sufficient details about how the attack could lead to data loss. As a result, the client might not prioritize fixing the issue, leaving the system exposed.

Conclusion

Penetration testing is a vital part of any organization's security program, helping to uncover vulnerabilities before they can be exploited. However, mistakes during the penetration testing process can lead to incomplete assessments, missed vulnerabilities, or unnecessary disruption to business operations. By properly scoping the test, adhering to rules of engagement, performing thorough reconnaissance, and focusing on post-exploitation, ethical hackers can avoid these common pitfalls. Clear communication of findings and manual validation of automated results are also crucial to providing a comprehensive and valuable assessment. By avoiding these common mistakes, penetration testers can ensure their efforts contribute meaningfully to strengthening the security posture of the organization.