Internal vs. External Penetration Testing: How Do They Differ?

Network Penetration Testing intentionally subjects systems and applications to malicious techniques, such as malware and other simulated cyber attacks, to test network security and their response to threats. Penetration Tests, or pen tests, identify vulnerabilities in a network and help to prevent future attacks and breaches. Pen tests are also referred to as white hat attacks or ethical hacking.

In this blog, learn more about Internal and External Penetration Testing, how they differ, the tools and methodologies used in them and how you benefit from them.

What is Network Penetration Testing?

 

Network Penetration Testing is the process of finding vulnerabilities on a network. A network is a group of computers and devices linked together by an IP address, which can be thought of as the web address for each computer. The goal of Network Penetration Testing is to find security dips that are prone to cyber attacks and data breaches that could be exploited by hackers.

Typically, Penetration tests use a variety of tools and techniques to assess systems, applications and networks. Below are the six main categories:

  1. Manual Testing - This method involves manually examining each system on the network to determine whether it has been compromised by hackers or not.
  2. Automated Tools - These tools perform most or all of the work involved in performing manual tests and then present their results in an easy to use format (usually as reports).
  3. Manual Audits - These are similar to automated tools, but rely on human judgement instead of automated processes. They are basically just like using an automated tool except you're doing it manually rather than using an automated tool.
  4. Hardware Penetration Tests - These tests use hardware to expose security weaknesses in a system. This is mostly seen in IoT (Internet of things) devices such as security cameras, networked printers and smart home systems.
  5. Software Penetration Tests - These tests use software to exploit weaknesses in a system or application. This is mostly seen in enterprise web apps, APIs, and software.
  6. Fuzzing - This is an approach where one tries to find weaknesses by creating a large number of random inputs to the target application with hopes that some will trigger bugs in the system.

Now that we have covered the types of tools and systems used in Network Penetration Testing, let us take a closer look at one of the areas often overlooked that apply to both internal and External Penetration Testing: ‘boxes of Penetration Testing’

What are the ‘boxes’ of Penetration Tests?

The ‘boxes’ of penetration tests are the parts of the system that are more technical and in depth and therefore have to be further analysed. They might be different from how a normal user would think of them but they are still a part of your target system.

  1. Black Box Testing - In this type of testing, you do not know what is inside the system until after you have completed the assessment. This approach is useful for large organisations with complex security policies and regulations, since it allows you to validate whether or not your findings match with those regulations.
  2. White Box Testing - With this type of testing, you can gain access to the source code so that you can examine how data flows through applications. This approach is great for organisations that want to be sure they are not breaking any laws or regulations while doing their assessment.
  3. Grey Box Testing - This approach allows us to look at vulnerabilities from both sides of the box when observing traffic between systems.

Now that we have learnt about the ‘boxes’ of Penetration Testing which is a more technical side of this topic, let us take a look at how these methodologies can be applied while learning about Internal and External Penetration Testing.

What is Internal Penetration Testing?

 

Internal Penetration Testing is performed directly on an organisation's internal networks and typically takes place after an External Penetration test. It is meant to reveal how a hacker, or threat actor, with inside access might exploit network vulnerabilities. Internal threats may be in the form of negligent employees, vendors or other insiders with malicious intent.

Weak or shared passwords, unencrypted shared data and insecure networks are all flaws, or threat vectors, frequently uncovered by Internal Penetration Testing.

Generally, the following are tested during Internal Penetration Testing:

  • Computer systems and mobile devices
  • Workstations
  • Networks and servers
  • Access points
  • Firewalls
  • Intrusion Detection Systems (IDS) and Intrusion Prevention Systems (IPS)
  • HVAC systems with internet connectivity
  • Cameras
  • Personnel

If any vulnerabilities are identified during internal or external pen testing, the tester subjects the systems to malicious activities and gauges the potential for damage and unauthorised access. For example, testers may intentionally spread malware, steal credentials or leak information to uncover vulnerabilities.

Internal and External Penetration Testing differ in methodology and goals. Let us take a quick look at external penetration testing.

What is External Penetration Testing?

 

External pen testing is performed on an organisation's public facing systems, wherein testers simulate malicious outside attacks to uncover security flaws. Therefore, testers mimic hackers who do not have proper access and permissions.

The goal of External Penetration Testing is to find out whether existing security controls provide sufficient protection against an external attack.

The following are usually tested during External Penetration Testing:

  • Configuration and deployment management
  • Identity management
  • Authentication and authorisation
  • Weak cryptography
  • Client side
  • Error handling

Internal Penetration Testing vs External Penetration Testing: How do they differ?

 

While they share the same phases, there are several factors that are different between Internal and External Penetration Testing:

External Penetration Testing Internal Penetration testing
Tester acts as malicious outsider Tester acts as malicious insider
Determines the effectiveness of perimeter security controls Determines what an attacker might achieve with initial access
Performed by third-party security professionals Can be done by an external party or by an internal party
Results are used to prevent and detect attacks Results are used to create a baseline of your network
Typically takes 2-3 weeks depending on the size and complexity of the system Typically takes 3-5 days, depending on the size and complexity of the system

While they pose individual benefits, Internal and External Penetration Testing are most effective when conducted together and regularly.

Why do you need both Internal Penetration Testing and External Penetration Testing?

 

Both internal and external penetration testing are crucial to the development of a strong network security program. Minor security flaws could lead to serious breaches and the loss or compromisation of sensitive information.

Therefore, it is important to identify weak links in your organisation’s internal components (passwords, procedures and devices etc.) as well as opportunities for unauthorised access from external threat actors. Regular Penetration Testing, paired with other risk and vulnerability assessments, can help your organisation stay on top of its network security and prevent malicious attacks.

Conclusion

 

Internal and External Penetration Testing are important for the security of any business. They can be used to determine whether or not a system is vulnerable to attacks from malicious users and hackers, and they can also be used to identify vulnerabilities that could allow an attacker to gain access to sensitive information or cause damage.

This type of testing is also useful for identifying weaknesses in your code or system architecture. For example, if you are looking for a vulnerability in a web application, this type of testing can help you analyse the source code and find out where there might be problems with the application.

If you’re interested in learning more about data protection and information security, read our guide on how to get started with ISO 27001 Certification.

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