Introduction
Picture this: Your company proudly finished its annual penetration test three months ago. The report was clean, you remediated the issues, management exhaled, etc.
Fast forward to today. A new vulnerability is released for a common piece of software. Your business uses this software on a day-to-day basis. Attackers start scanning the internet for unpatched systems just hours after the vulnerability is published. Your company? You don’t even know you are at risk until it is too late.
This is the risk of a one-off penetration test — it opens you up for risk, in between penetration tests. This is also why many security teams are moving to Continuous Penetration Testing (CPT).
But one question we hear all the time
“Should continuous penetration testing be black box or white box?”
It’s an important question that will decide whether you will afford yourself real-world protections or squander all of your resources. Let’s discuss why it matters right now — and what approach makes the most sense.
What is Continuous Penetration Testing (CPT)?
Continuous penetration testing is ongoing security testing that finds and fixes vulnerabilities in real time.
Traditional penetration testing is like a yearly health checkup. It’s useful to get done every year. You wouldn’t wait a year for a doctor when your health declines suddenly. In the same way, you wouldn’t want to wait months for your attack surface exposure to be evaluated.
CPT is no different. Instead of performing a pentest once or twice a year, CPT provides you with:
- Always-on vulnerability identification: We use automated tools that continuously scan for newly introduced risk.
- Scheduled attack simulations: We use manual testers to conduct scheduled exploitation attempts to confirm findings.
- Real-time issue reporting: When an issue is identified, it is flagged promptly. This prevents waiting a few months for the pentest report to come out in a PDF.
- Constant risk visibility: your security team is always on top of their current attack surface.
This approach is critical, because threat actors are always evolving and they don’t wait for your next pentest window.
Black Box Testing
Black box testing is an attack, like a real hacker conducts a targeted attack, with no insider knowledge.
Why Black Box Fits CPT Perfectly
Black box testing is a natural fit for continuous penetration testing because it mimics:
- External Attack Surface: Moving targets on the internet. The testers are going look for vulnerabilities in your internet-facing systems, APIs, and applications.
- Real-World Exploitation: There are no credentials or architecture diagrams required — just like a hacker.
- Repeatable: A pen test can easily be synthesized to repeat across many assets, even if the environment changes.
- Automation-Friendly: All of the tests can be automated; this works easily with CI/CD and vulnerability scanners.
Example
A black box test discovers an exposed API endpoint. This is a new attack vector. It gives unauthorized access to protected data. The exposed endpoint is at risk because it’s continually aligned with the CPT plan. A scheduled six-month red team test will lead to its discovery.
White Box Testing — Intense but Challenging
White box testers take full advantage of what they have access to — source code, login details, and network architecture.
Benefits of White Box Testing
- Comprehensive Coverage: Who knows what else is lurking within the internal structure that needs attention.
- Mastery of the Code Level: Excellent for secure code reviews and audits driven by compliance and requirements.
- Early Stage Security: Very good when testing applications before deploying them to production.
Why it’s Hard to Use Continually
Why is the white box testing technique so powerful and helpful but hard to use continually:
- Constantly Learning: Every new code and/or architecture revisions need reso-memorizing as the details must fully re-shared again
- Expensive Execution: Manual deep-diving takes time thus takes longer to report out.
- Time Consuming: Expensive when many senior engineers need similar amounts of processing time.
Before comparing testing types, it helps to understand the basics — see What Is Continuous Penetration Testing?.
Black Box vs. White Box: Choosing What Works Best for CPT
Here’s how the two compare for continuous penetration testing:
| Factor | Black Box (Best for CPT) | White Box (Use Selectively) |
| Realism | Simulates real-world attacker behavior | Simulates insider threat scenario |
| Scalability | Highly scalable, repeatable | Harder to scale — needs constant updates |
| Speed | Fast to execute, easy to automate | Slower, more manual effort |
| Cost | Cost-effective for ongoing use | Higher cost for frequent runs |
| Best Use Case | Ongoing attack surface monitoring | Periodic code review, compliance audits |
Black Box + White Box: The Balanced Approach
The best approach is not to pick one over the other, but to leverage both at their core competencies:
Continuous Black Box Testing: Continuous oversight of what attackers can see, 24/7.
Targeted White Box Testing: Security of your internal systems and code at logical checkpoints.
Doing this lets you get more appropriate, budget-friendly security coverage without overtaxing your team or financial resources.
Still deciding between one-time vs. continuous security assessments? Read our full breakdown of Continuous Penetration Testing vs. Traditional Pen Testing.
Conclusion
Relying on your pentests as a once-and-done infosec solution is risky. It’s like leaving your front door unlocked most of the year. You only check it occasionally.
Continuous pen testing, supported by an ongoing black box approach, ensures your defenses are regularly challenged. Still, this is conducted by organizations intending to find weaknesses, not to help you improve. Augment that with a few targeted white box tests, and you will have a solid, balanced security program.
Learn how your business can strengthen its defenses with Encyb’s Continuous Penetration Testing Services.
FAQs
1. What is the biggest difference between black box and white box testing?
The main difference is visibility. Black box testing is performed without insider knowledge, simulating an external hacker’s perspective. White box testing gives testers full access to systems, code, and documentation, allowing them to find deeper vulnerabilities.
2. Does continuous penetration testing replace traditional annual pentests?
Yes and no. CPT reduces the need for one-time pentests. It constantly monitors and tests your systems. Still, many companies do an annual or semi-annual audit for compliance or reporting requirements.
3. How is CPT different from vulnerability scanning?
Vulnerability scanners only find known weaknesses. Continuous pentesting goes further. It attempts to exploit vulnerabilities to confirm if they are truly exploitable. This process reduces false positives. It also prioritizes real risks.
4. Is continuous penetration testing expensive?
It can actually save money compared to running multiple manual pentests per year. By focusing on black box testing and automating routine checks, CPT offers ongoing protection at a predictable monthly cost.
5. How Often Should We Run White Box Tests?
Typically every 6–12 months, or after major system upgrades, code deployments, or regulatory requirements.
6. Can We Use Both Black Box and White Box Testing Together?
Yes — and it’s often recommended. Many mature security programs use continuous black box testing for daily protection. They also use scheduled white box testing for major releases or compliance requirements.
7. Is Black Box Testing Enough on Its Own?
For continuous external threat detection, yes. White box testing remains valuable. It catches deep, internal flaws. Attackers exploit these flaws if they ever gain a foothold.
8. Can CPT test cloud environments and APIs?
Absolutely. Modern CPT platforms support cloud infrastructure, APIs, web apps, and SaaS platforms. They guarantee your entire attack surface is covered. This includes more than just on-prem systems.
9. How quickly do we get results from CPT?
Unlike traditional pentests that deliver a single report weeks later, CPT provides findings in real-time or near-real-time. This allows your team to start remediation right away.
10. Is black box testing safe for production systems?
Yes — when done professionally. CPT uses controlled, safe exploitation techniques that avoid disrupting production environments. You still get realistic results without risking downtime.
11. Do we still need a red team if we have CPT?
Red teaming focuses on advanced, targeted attacks (often stealthy and goal-based), while CPT focuses on continuous surface-level exposure testing. Many organizations use both — CPT for daily monitoring, red teams for advanced scenarios.
12. What compliance frameworks gain from CPT?
CPT supports frameworks like ISO 27001, SOC 2, PCI-DSS, HIPAA, GDPR. It provides ongoing evidence of security testing. It also demonstrates remediation efforts.
