Building a resilient cybersecurity strategy begins with a clear understanding of your environment – both the systems exposed to the outside world and those operating within your internal network. Penetration testing plays a vital role in uncovering opportunities to strengthen your organization’s security posture before vulnerabilities can be exploited.

Among the different types of assessments, internal and external penetration testing address distinct areas of risk. Knowing their differences helps organizations prioritize efforts and build a well-rounded security strategy.

In this article, we’ll walk you through the key distinctions between internal and external penetration testing, when each approach is most valuable, and how combining them can maximize your resilience.

What is Penetration Testing?

Penetration testing, often referred to as ethical hacking, is a proactive security assessment where trained professionals simulate real-world cyber attacks to identify vulnerabilities in systems, applications, or processes. The goal is to uncover potential weaknesses before malicious attackers can exploit them – and to provide actionable recommendations for strengthening defenses.

Penetration testing service differs from vulnerability assessments by actively exploiting vulnerabilities under controlled conditions, rather than simply identifying them. If you’re interested in learning more about this distinction, we explain it in detail in our guide on Vulnerability Assessment vs Penetration Testing.

Additionally, if you’re wondering why penetration testing is essential for all businesses, we cover the key benefits in our article Why Penetration Testing Is Important.

What is Internal Penetration Testing?

Internal penetration testing assesses the security of your organization’s systems and data from within the trusted network perimeter. It simulates scenarios where an attacker already has some level of internal access – for example, through a compromised employee account, potential insider threats, or a previously successful external attack.

Key areas of focus include:

• Privilege escalation: Testing whether standard user accounts can gain unauthorized access to internal systems or sensitive data.
• Lateral movement: Evaluating how easily an attacker could move across network segments to access sensitive data and valuable resources.
• Sensitive data exposure: Checking the accessibility of confidential files, credentials, and business-critical systems.

Typical targets in an internal penetration test:

• Internal servers and file shares
• Active Directory and authentication systems
• Employee workstations and internal web applications

By conducting internal penetration testing, organizations gain insight into the effectiveness of network segmentation, access controls, and internal monitoring to uncover internal vulnerabilities – all critical elements for strengthening cybersecurity resilience.

What is External Penetration Testing?

External penetration testing focuses on assessing systems that are exposed to the internet – essentially, everything that a potential attacker could access remotely. It simulates external attackers attempting to identify potential weaknesses and gain a foothold into your network.

Common targets include:

• Public-facing websites and web applications
• Email, VPN, and DNS servers
• Remote access portals and cloud services

An external penetration test typically involves steps like reconnaissance, vulnerability analysis, and carefully controlled exploitation to uncover gaps that could be used to breach the network from the outside.

Organizations seeking a structured, standards-based approach to penetration testing should also consider certifications like CREST. Learn more about this quality benchmark in our overview of The Power of CREST-Certified Penetration Testing.

Key Differences Between Internal and External Penetration Testing

While both internal and external penetration tests aim to uncover vulnerabilities, they focus on different types of threats and require distinct approaches. Here’s a quick overview of how they compare:

Understanding these differences is key to building a comprehensive cybersecurity strategy that protects both your internal environment and your external-facing systems.

When Should You Choose Internal Penetration Testing?

Internal penetration testing is particularly valuable in scenarios where:

• You want to simulate insider threats. Whether malicious or accidental, employees can pose security risks.
• Your organization has undergone significant changes. Restructuring, mergers, or onboarding new technologies can introduce new vulnerabilities.
• You aim to validate internal segmentation and access controls. It’s important to ensure that compromised credentials do not allow unrestricted movement.
• Compliance requirements demand it. Many regulations (like PCI DSS, HIPAA, or ISO 27001) expect organizations to assess internal security controls regularly.

Regular internal testing helps organizations stay resilient even after an external perimeter has been breached – closing the security gaps attackers could exploit internally.

If your business operates software platforms or complex IT environments, internal pen testing is especially critical. Our article Why Software Companies Need Penetration Testing explores this need in more detail.

When Should You Choose External Penetration Testing?

External penetration testing is ideal when you need to:

• Protect internet-facing systems. Public websites, APIs, VPN gateways, and remote access systems are prime targets for attackers.
• Launch new digital services. Before going live with new applications or platforms, it’s crucial to identify vulnerabilities threatening your external defense.
• Meet compliance requirements. Frameworks like PCI DSS often require external network penetration tests for public-facing assets.
• Maintain customer trust. Demonstrating that you proactively secure your online presence strengthens brand reputation.

External penetration testing is typically the first line of defense, helping organizations stay ahead of constantly evolving external threats.

Choosing a trusted partner for your assessments is critical. For guidance on this, you might find our post on How to Find the Best Penetration Testing Provider helpful when planning your next test.

Can You Combine Both?

The most effective cybersecurity strategies integrate both internal and external penetration testing to prevent data breaches. By combining them, organizations gain a complete view of their security posture – from perimeter defenses to insider risk mitigation.

Comprehensive testing ensures that:

• Attackers cannot easily breach external systems.
• If external defenses fail, internal controls effectively contain the threat.
• Compliance requirements are fully addressed across multiple domains.
• Overall risk exposure is minimized, boosting resilience and readiness.

At AMATAS, we tailor penetration testing programs based on the unique needs of each client, ensuring full coverage across all potential attack surfaces, including both internal and external threats.

How AMATAS Helps You Stay Secure

At AMATAS, we understand that every organization faces unique cybersecurity challenges. Our penetration testing services are designed to address both external and internal threats with precision and expertise.

Our team of certified ethical hackers brings extensive experience across multiple industries, helping businesses identify vulnerabilities that could otherwise go unnoticed. We tailor each engagement to the organization’s environment, ensuring that the scope, depth, and approach of testing align with your specific risk profile and business objectives.

Whether you need to validate your external perimeter, assess internal controls, or build a comprehensive testing program that covers both, AMATAS is equipped to support your goals. Our methodology combines technical excellence, a deep understanding of compliance requirements, and a commitment to actionable reporting – empowering you to make informed security improvements.

Ready to strengthen your defenses? Request a consultation with our experts and find out how we can help you build a more secure future.

Conclusion

Internal and external penetration testing each play a vital role in uncovering different types of security risks. While external tests focus on preventing unauthorized access from the outside, internal tests ensure that attackers cannot easily move within your network if they manage to get in.

A balanced, proactive approach that incorporates both types of testing is key to building a resilient cybersecurity posture. By identifying and addressing vulnerabilities before they are exploited, organizations can prevent costly data breaches, protect their reputation, and stay ahead of evolving threats.

Talk to our experts at AMATAS to design the right penetration testing strategy for your organization – one that not only meets today’s challenges but also strengthens your readiness for the future.

FAQs

What are the three 3 types of penetration test?

The three main types of penetration tests are black box (no prior knowledge of the target), white box (full knowledge of the target), and gray box (partial knowledge). Each approach offers different insights depending on the organization’s security goals and risk profile.

What is external penetration testing?

External penetration testing assesses the security of publicly accessible systems such as websites, VPNs, and cloud services by simulating attacks from outside the organization. It focuses on preventing unauthorized access to your internal network through internet-facing vulnerabilities, which is crucial for maintaining the organization’s perimeter security .

What is internal penetration testing?

Internal penetration testing evaluates the security of systems and processes inside the organization’s firewall, simulating scenarios like insider threats or post-breach movements. It helps identify security weaknesses in access controls, network segmentation, and data protection practices.

Should software companies prioritize internal or external penetration testing?

Software companies should prioritize both, but typically start with external penetration testing to secure public-facing platforms and APIs. Internal testing becomes crucial when protecting sensitive customer data, intellectual property, and ensuring secure software development environments.

Can penetration tests be integrated into our SDLC or DevSecOps workflows?

Yes, penetration testing can be integrated into SDLC and DevSecOps workflows to identify vulnerabilities early in the development process. Incorporating regular testing during pre-deployment stages helps create more secure applications and reduces costly fixes later.

What type of penetration testing is required for financial compliance standards like PCI DSS or DORA?

Financial compliance standards like PCI DSS and DORA typically require both external and internal penetration testing to validate system security. Regular tests of critical systems, applications, and networks help maintain compliance and mitigate regulatory risks.

Can penetration testing help us meet HIPAA security requirements?

Yes, penetration testing helps meet HIPAA security requirements by identifying vulnerabilities that could expose protected health information (PHI). Regular testing strengthens technical safeguards and supports risk analysis obligations under the HIPAA Security Rule.

What support does AMATAS provide after the tests – will we get help with remediation and reporting?

After testing, AMATAS provides detailed reporting, executive summaries, technical recommendations, and remediation support. We work closely with clients to prioritize fixes, understand vulnerabilities, and strengthen overall security posture based on real-world risk exposure.

How does AMATAS tailor penetration testing to our specific industry risks?

AMATAS tailors penetration testing based on your industry’s threat landscape, compliance requirements, and operational needs. Whether in healthcare, finance, software, or other sectors, we customize testing methodologies to align with your business-specific security objectives.