Table of Contents

• Penetration Testing: How choose between Black Box, Gray Box, and White Box?
  • What Is a Penetration Test?
  • Penetration Testing Approaches
    • Black Box Penetration Test
      • Black Box Methodology and Process
      • Black Box Techniques
    • Gray Box Penetration Test
      • Gray Box Methodology in Depth
      • Practical Gray Box Scenarios
    • White Box Penetration Test
      • White Box Analytical Approaches
      • Specialized White Box Tools and Techniques
  • Comparison and Method Selection
    • Main Decision Factors
  • Conclusion
  • Our services

Penetration Testing: How choose between Black Box, Gray Box, and White Box?

Cybersecurity holds a central position in the strategies of many organizations. Between protecting sensitive data, safeguarding a company’s reputation, and complying with prevailing regulations, each decision aimed at strengthening information system security is crucial. In this context, penetration tests — also known as pentests — stand out as an effective way to assess the resilience of an infrastructure against malicious attacks.

In this article, we will explore the three major pentest approaches: Black Box, Gray Box, and White Box. We will also examine how to select the most suitable method according to your company’s context and the types of threats you need to address.

What Is a Penetration Test?

A penetration test is a simulated cyberattack conducted by cybersecurity experts (pentesters) to evaluate how well an information system can withstand real threats. In practical terms, the pentester employs various techniques (vulnerability scans, exploiting flaws, social engineering, etc.) to identify weaknesses in the infrastructure and then provides suitable recommendations.

Penetration tests enable organizations to:

• Prevent attacks: By fixing weaknesses before they can be exploited by real cybercriminals.
• Test defenses: Evaluate the effectiveness of firewalls, intrusion detection systems, and authentication measures.
• Comply with regulations: Many standards (ISO 27001, GDPR, PCI-DSS, etc.) require regular security testing.
• Bolster trust: Reassure clients and partners by ensuring the security of critical data.

Regarding methodology, the amount of information provided to the pentester prior to the test varies. Based on this criterion, penetration tests are classified as Black Box, Gray Box, or White Box.

Penetration Testing Approaches

Black Box Penetration Test

A Black Box penetration test closely simulates an external attack by a cybercriminal who has no prior knowledge of the target.

Black Box Methodology and Process

1. Passive Reconnaissance
   The pentester gathers all publicly available information (WHOIS databases, DNS, social networks, data leaks, etc.).
2. Scanning and Enumeration
   Using analysis tools (Nmap, Shodan, etc.), the pentester takes inventory of open ports, active services, and software versions in use.
3. Vulnerability Analysis
   The collected data are cross-referenced with vulnerability databases (CVE, exploit-db, etc.) to identify potential known exploits.
4. Exploitation
   Detected vulnerabilities are exploited to breach the system, bypass security measures, and gain access to critical resources.
5. Post-Exploitation and Reporting
   Once the system is accessed, the pentester determines how far they can move within it (lateral movement, data exfiltration, etc.). Finally, a detailed report is provided, listing vulnerabilities along with recommended fixes.

Black Box Techniques

• Vulnerability Scanners: (Nessus, OpenVAS, etc.) for common flaw detection.
• Brute Force Attacks: To test the strength of credentials and passwords.
• Social Engineering: Exploiting human weaknesses via phishing or manipulation tactics.
• Zero-Day Exploits: Searching for unknown and unpatched vulnerabilities.

Key Advantage: Delivers maximum realism by placing the pentester in the role of an attacker with no special access.
Limitation: Can be more time-consuming and resource-intensive to yield conclusive results, especially for complex infrastructures.

Gray Box Penetration Test

The Gray Box penetration test lies between Black Box and White Box. Here, the pentester has some basic knowledge about the system: limited user access, network topology, relevant domains, software versions in use, and so on.

Gray Box Methodology in Depth

1. Receiving Preliminary Information
   The client provides some details (IP addresses, low-privilege accounts, etc.) to guide the pentester.
2. Targeted Analysis
   Using these initial data, the pentester focuses on the most critical areas (internal applications, sensitive databases, administrative interfaces).
3. Combining Multiple Techniques
   Both Black Box (external scanning) and White Box (internal checks) techniques are employed for a more nuanced mapping of the infrastructure.
4. Focused Exploitation
   Attacks are more precise because the pentester already knows certain elements (hostnames, network architecture, low-privilege credentials, etc.).

Practical Gray Box Scenarios

• Internal Web Application: A standard user account is provided to identify privilege escalation opportunities or SQL injection flaws within the member area.
• Enterprise Network: The pentester knows how the internal network is segmented, including VLANs, enabling targeted attacks on critical servers.
• Partial Source Code Access: The pentester has some code segments to better understand business logic and identify configuration errors or logical flaws.

Key Advantage: Strikes a balance between efficiency and realism. The tester goes to the heart of the matter faster than in Black Box testing, while retaining an approach akin to a real attacker.
Limitation: The partial information provided can slightly skew the tester’s view, who is no longer entirely in the dark like a true external attacker.

White Box Penetration Test

A White Box penetration test (also referred to as Clear Box or Glass Box) is the most comprehensive approach. In this scenario, the pentester has all relevant details about the target: architectural diagrams, documentation, source code, databases, administrative accounts, and more.

White Box Analytical Approaches

1. Source Code Review
   Detailed analysis to uncover security flaws such as injections, logic errors, or weak cryptographic practices.
2. Architecture Review
   In-depth study of the infrastructure (servers, APIs, microservices) to spot inconsistencies and design vulnerabilities (poor segmentation, unencrypted protocols, etc.).
3. Configuration Analysis
   Verification of security settings (firewalls, ACL rules, account and password management, audit logs, etc.).
4. Security Unit Testing
   Integrating automated testing into the development lifecycle (CI/CD) to detect vulnerabilities as soon as they appear.

Specialized White Box Tools and Techniques

• Static Application Security Testing (SAST): Tools like SonarQube, Fortify, Checkmarx, etc.
• Dynamic Application Security Testing (DAST): Simulated attacks in controlled environments to observe the real-time behavior of applications.
• Reverse Engineering: Disassembling binaries (or any code not provided) to understand internal functionalities.
• Advanced Penetration Tests: Simulating advanced persistent threats (APT) or malicious insider scenarios.

Key Advantage: Identifies deep-seated vulnerabilities and offers a comprehensive view of the system’s security posture.
Limitation: Requires a high level of trust from the company and advanced expertise from the pentester to interpret the large volume of data.

Comparison and Method Selection

Choosing between Black Box, Gray Box, and White Box involves balancing realism, execution speed, and depth of analysis:

Main Decision Factors

• Test Objectives
  Are you aiming to simulate an unknown hacker (Black Box) or obtain a complete analysis of your systems (White Box)?
• Budget and Time
  White Box and Gray Box can be more cost-effective timewise because the discovery phase is streamlined.
• Trust and Confidentiality
  Sharing all your source code or architectural documents requires a strong level of confidence in the pentesting team.
• Cybersecurity Maturity Level
  A company that already has solid security measures might opt for a Black Box test to evaluate its perimeter defenses. Conversely, an organization aiming to scrutinize every corner of its infrastructure might choose a White Box test.

Conclusion

Black Box, Gray Box, and White Box penetration tests represent three complementary facets of a holistic cybersecurity strategy. Their implementation allows organizations to:

• Identify vulnerabilities and remediate them quickly.
• Boost confidence among clients, partners, and regulatory bodies.
• Continuously enhance development processes and configurations.
• Gain peace of mind in the face of evolving cyber threats.

The best strategy often involves combining these approaches. For example, you could start with a Black Box test to uncover urgent external vulnerabilities, follow up with a Gray Box test to assess internal robustness, and finish with a White Box test to refine the security of your code and overall architecture.

By offering a tailored mix suited to each organization’s reality, penetration testing becomes an essential ally in pursuing robust and sustainable security.

Our services

We are a team of dedicated cybersecurity consultants focused on uncovering weaknesses and helping organizations strengthen their security posture.

We ensure confidentiality with encrypted communications via pgp and accept any confidentiality clauses you may propose.

We are specialized in pentesting, code auditing and monitoring to ensure the security of your services and infrastructure.

You can contact us at [email protected] if you have any questions or need help with your cybersecurity needs, or directly submit your project to our contact form.