Routine scans find surface flaws. Pentests expose what actually breaks when a real attacker pushes your defense. To understand your security posture without illusions, you run the right penetration test — internal, external, or both.
Penetration testing simulates a real-world attack on your systems, allowing you to identify potential vulnerabilities and weaknesses. But what kind of penetration test does your organization need?
There are seven types of penetration testing, each designed to uncover different classes of risk and each offering its own strategic advantages. Internal and external penetration tests form the foundation, covering both the inside and outside of your environment, while the other testing types deliver focused insights that complete the full security picture.
External = attacks from outside the perimeter.
Internal = attacks from inside the network.
Both matter. Each tells a different part of the story.
Knowing when to deploy each type of test is key to an efficient defense. But what are the differences, when should you use which one, and what results can you expect? Here, we’ll discuss internal vs. external penetration testing and when you might need them.
Internal vs. External Testing at a Glance
Short Answer: Which Pentest Do You Need?
External Penetration Test
Use this when you want to secure public-facing systems, protect web applications, or meet compliance mandates such as PCI DSS.
It answers: "Can they get in?"
Internal Penetration Test
Use this when you’re operating in assumed-breach mode or validating segmentation and insider-risk exposure.
It answers: "Once they are in, how far can they get?"
Layered Penetration Test
Use this when you want the real, full impact of a targeted attack, from initial breach through internal escalation.
It answers: “What’s the total damage?”
What Is External Penetration Testing?
External penetration testing evaluates how an outside attacker might compromise your internet-facing systems.
It simulates an attacker starting from zero-access, probing only what the world can see: your websites, VPNs, firewalls, email servers, and other perimeter assets.
The terms "external penetration testing" and "external network penetration testing" are often used interchangeably. Critically, when discussing scope during interviews with penetration testing companies, you must confirm which external systems will be tested to ensure alignment with your specific security objectives.
External penetration testing involves:
- A defined pentest framework and clear objectives
- Identification of vulnerabilities in public-facing applications and systems
- Simulated attacks using targeted OSINT and perimeter footprinting
- Testing techniques such as OWASP-aligned application assessments, password spraying, and firewall exposure evaluation
- Reporting with practical remediation steps.
An external network is like someone circling your house, checking every door, window, and hinge for weak points. Even a hairline crack becomes an opportunity.
Keep in mind that an external pentest is focused, methodical, and thorough — but it’s not deep red-team espionage.
Proving the Risk: Our "Offense is the Best Defense" Methodology
At Mitnick Security, we test your perimeter like a real attacker. Then we show you exactly what could be stolen or disrupted.
The Global Ghost Team™, our elite pentesters, uses attacker-grade tactics. When a vulnerability is exploited, we trace the impact, including data exposure, operational risk, and the next logical steps in potential attacks.
External network penetration tests can be time-intensive and complex, especially when done correctly. It can take specialists 2 to 3 weeks to complete an external pentest. At Mitnick Security, we take our role seriously, and we conclude testing only after we successfully simulate a data breach.
After this point, an internal penetration test would provide insight into how far a threat actor could go into your systems.
What Is Internal Penetration Testing?
Internal penetration testing evaluates what an attacker can do after they gain access to your internal network.
It simulates either a malicious insider or an external attacker who has already breached your perimeter.
Internal penetration testing, also called an internal network assessment, simulates an attack from within your organization’s network to identify vulnerabilities in internal systems, software, and user privileges. This assessment mimics the permissions an employee might have or the access a threat actor gains after breaching your external defenses.
The terms "internal penetration testing" and "internal network penetration testing" are often used interchangeably. When evaluating vendors, ask what assets and systems their test will include, and confirm that the defined scope aligns with your expectations.
The Critical "Assumed Breach" Scenario
At Mitnick Security, we operate on an "assumed breach" model, assuming an attacker has already compromised a user’s workstation via phishing or credential theft. We then attempt to move laterally, escalate privileges, and access the "crown jewels" of your data.
Optimized Internal network penetration testing involves:
- A defined pentest framework and targeted objectives
- Identification of vulnerabilities in internal applications and systems
- Lateral movement attempts
- Privilege escalation testing
- Internal scanning, exploitation attempts, and firewall evaluation
- A report of findings so your organization can tackle remediation steps
In most cases, the goal of a pentest is to determine how easily an intruder can gain access to confidential information. These engagements can take up to 3 weeks, and they often last anywhere between 3 to 6 weeks. Although internal penetration tests are a greater monetary investment, they provide a full scope of how threat actors can move laterally through your system if they were to gain internal access to your network.
Internal pentests can also be combined with other tests, such as social engineering and phishing attacks, to provide a more comprehensive view of your security status.
Which Penetration Test Is Best for Your Organization?
Prioritizing the right test depends on your current security maturity and immediate business triggers. Here is how to decide which assessment fits your needs.
Choose an External Pentest if…
- You’ve already experienced an external data breach and are looking to improve your security.
- You’ve recently launched new public-facing websites, applications, FTP servers, and more.
- You are required to meet specific compliance mandates (e.g., PCI DSS, HIPAA, SOC 2).
- You’ve done routine testing, such as vulnerability scans, but have never had a true test of your perimeter security.
Prioritize an Internal Pentest if…
- You want to validate controls against an "assumed breach" or insider threat.
- You are implementing a Zero Trust architecture and need to verify segmentation.
- You’ve had an external penetration test and want to see how far a threat actor could get inside your system.
- You suspect your infrastructure may be insecure.
- Your employees may not have been trained in cybersecurity awareness, leaving them vulnerable to user escalation points.
The Full-Spectrum Approach: Layering Both Tests
If you want a comprehensive view of how a threat actor could breach your external security and what they can do once inside your network, an internal network penetration test can be combined with external network testing.
With back-to-back testing, you’ll get a comprehensive view of your cybersecurity posture and experience minimal interruptions to your daily operations. This allows you to simultaneously evaluate the reports from these tests and prioritize the most important remediation steps.
Is It Time To Test Your Cybersecurity Posture?
Since the difference between internal and external penetration testing centers on “where” it occurs, it’s crucial to identify which areas of your organization require a deeper examination.
After all, you can’t defend what you don’t understand. Whether assessing your perimeter or your internal segmentation, Mitnick Security provides the elite expertise required to uncover hidden risks through pentesting. Once you understand the security level of your organization and its vulnerabilities, you can prevent devastating attacks on your business.
Don't wait for a breach to test your defenses. Take our free Pentesting Readiness Assessment to discover which penetration test is right for you.
