Internal Network Penetration Testing: Identify Vulnerabilities Before Attackers Do

Cyber threats often focus on vulnerabilities that remain overlooked. Internal network penetration testing evaluates the security of internal infrastructure from the perspective of an attacker who has already gained access to the network or operates from within.

This approach reveals weaknesses and helps prevent attacks by simulating real scenarios, such as the actions of an attacker who has gained access to the network or internal risks related to the compromise of employee accounts. In this article, we will explore why internal network pen testing is crucial and how to implement it effectively.

What is an internal network penetration test?

Internal network pen test is an assessment of the security of an organization's internal infrastructure. It aims to uncover deficiencies and weaknesses in network configuration, target systems, web applications, and permissions that could be exploited by malicious actors. The test simulates the actions of a hacker who has gained entry to the infrastructure or an employee with legitimate access rights.

The primary goal of this pen test is to identify and remediate weaknesses to protect data, internal systems, and prevent data leakage. This penetration test type analyzes threats that arise within the organization, such as those posed by compromised devices or employee actions.

Pen test is critically important for strengthening security, ensuring compliance, and protecting sensitive data from potential risks.

Why is internal network penetration testing important?

Regular internal network penetration testing advantages

A pen test can provide significant benefits to an organization. It allows you to significantly improve data protection. By detecting vulnerabilities that can be exploited by attackers or compromised accounts, you can keep your data safe. Additionally, it serves as an excellent way to comply with industry regulations, most of which require organizations to conduct regular security assessments to protect customer data. With an evaluation of internal security effectiveness, you can implement effective mitigation strategies and safeguard your clients.

Consequences of not having a pen test performed

Failure to perform a penetration test can have serious consequences, such as system breaches, loss of trust from clients and partners, and financial and operational losses for the business. Organizations may remain unaware of critical deficiencies that could be exploited by hackers if such assessments are not conducted. It’s important to recognize the significant risks to clients in terms of potential system compromise and data exfiltration, which could result in unauthorized entry.

Importance of regular internal network pen testing

Regular penetration tests are essential for verifying the remediation of identified deficiencies and maintaining an appropriate level of cybersecurity. Cyber threats evolve frequently, and new deficiencies may emerge in updated systems and web applications. Such regular pen tests allow organizations to stay ahead of the curve and ensure that new vulnerabilities are addressed in a timely manner.

Preparation for internal network penetration test

Preparing for an internal penetration test is a complex yet essential procedure that requires careful planning and coordination. The effectiveness of each stage impacts not only the security of data systems, but also the organization's overall resilience to cyber threats. Here are some main aspects to consider during preparation:

1. Defining pentest goals and scope

Before conducting the pen test, it's crucial to perform a preliminary risk assessment to understand which data and systems are most critical. This focus allows you to uncover the most vulnerable and important components. You can then set clear objectives and choose the targets for the penetration test, such as servers, workstations, database management, internal web applications, or devices like routers and switches.

2. Engaging and preparing a team of specialists

An experienced team of professionals with expertise in internal network penetration test can significantly enhance vulnerability detection for the organization. This team may include external specialists with relevant certifications (e.g., CEH, CISSP, eWPT).

3. Preparing the environment

Before the penetration test, create backups of important data to allow for quick recovery in case of issues within. Inform staff about the planned activities to avoid panic and ensure system stability by avoiding active changes.

4. Choosing a pen test approach

Establishing a clear pen test approach is a critical step in preparing for internal network penetration testing. Approaches can vary: a “black-box” approach means pentesters have no information about the system; a “gray-box” approach means pentesters have limited data; and a “white-box” approach provides pentesters with full visibility into information.

5. Access and documentation acquisition

Depending on the chosen approach and agreements, ensure that all necessary entry to systems is obtained, including IP addresses, servers, workstations, and network devices. This access enables pentesters to perform their tasks effectively and conduct a comprehensive analysis. Additionally, it’s important to provide documentation that includes data about system configurations and network architecture.

6. Legal and ethical considerations

Consider international standards, legal, and ethical norms related to penetration testing. Obtain all necessary permissions and coordinate actions with the organization's management, discussing any prohibitions (e.g., data deletion or servers reboots).

7. Preparing reporting criteria

Before starting the pen test, define success criteria and report formats. This clarity will help present the findings of the pentesting and recommendations for improving protection effectively.

In conclusion, all these aspects should be discussed with the client to ensure a clear understanding of goals and expectations, as well as to consider specific client requirements and preferences.

Steps of internal network penetration testing

Step 1: Information gathering

In this initial phase, pentesters collect all available information. This may include data on network devices, systems, internal web applications, and users. The goal of this stage is to create a comprehensive picture of the network architecture of the organization, which helps identify potential deficiencies.

Step 2: Reconnaissance

Pentesters' team perform both passive and active discovery to determine which systems and services are operational within the network. They may use various tools to scan the network for available resources such as servers, workstations, and network services.

Step 3: Detection and scanning 

This stage involves both static and dynamic analysis. Static analysis examines software code to uncover deficiencies. In contrast, dynamic analysis tests the system in real-time to observe its behavior under load. Both approaches help uncover weak points.

Step 4: Vulnerability assessment

The pentesters analyze the identified deficiencies, assess their severity and risks, and prioritize them for remediation.

Step 5: Exploitation

At this stage, testers try to exploit vulnerabilities to see how easily an attacker can gain access to the system. The purpose of this stage is to confirm the existence of vulnerabilities and determine the real level of danger.

Step 6: Final analysis and review

After conducting the internal network pen test, pentesters analyze the gathered data and prepare a report outlining the identified vulnerabilities, exploitation methods, and recommendations for remediation. This stage is crucial for providing a full understanding of the organization's cybersecurity posture.

Step 7: Lateral movement in the network

This step is particularly relevant for assessing defenses against attacks using compromised credentials. It involves checking for lateral movement capabilities after gaining entry to one system: can hackers navigate between different resources to expand access to sensitive information?

Step 8: Privilege escalation

At this stage, pentesters attempt to get administrative rights or access to critical systems by exploiting deficiencies. The aim is to demonstrate how a harmful actor could take control of key resources in the organization.

Step 9: Utilizing pen testing results

The primary goal of this final stage is to mitigate risks and strengthen defenses against threats. This includes implementing recommended changes, training staff within the organization, and continuously monitoring systems.

The 3 main challenges of internal network penetration testing

Internal network pen test can face a number of challenges that complicate the process of identifying deficiencies. Let's take a look at some of the main problem areas and how to overcome them.

1. Complicated network structures

Today's organizations often have complex infrastructure architectures that include multiple segments, subnets, and virtualized environments. This complicates the task of pentesters, who must have a deep understanding of the network's architecture.

How they take this challenge into account:

• Documentation. Before the test, it's important to have clear documentation of the network structure to help examiners understand which components and connections need to be tested.
• Pen test segmentation. Pentesters can divide every test into phases, focusing on individual network segments to better manage complexity.

2. Restricted access

Access to certain data may be restricted due to cybersecurity policies or lack of rights. This makes it difficult to uncover deficiencies, as pen testers may not be able to evaluate all aspects of the system.

How they take this challenge into account:

• Collaboration with teams. Pen testers must work closely with the IT department to gain the necessary access. This may include creating accounts with elevated rights for testing.
• Using a gray-box. Tapping into some of the system's information (e.g., configurations and documentation) can help pen testers adapt their methods to access restrictions.

3. The need for manual verification

Automated tools can detect many deficiencies, but some issues require manual testing for detailed analysis. This may include complex logic deficiencies that cannot be detected by automated scanners alone.

How they take this challenge into account:

• A combination of automation and manual test. Penetration testing typically follows a hybrid approach, first automating the detection of basic deficiencies and then moving on to manual test for deeper analysis.
• Training of pentesters. Regular training and certification of security professionals helps them maintain up-to-date knowledge of new deficiencies and pen testing methods.

Penetration test faces numerous challenges. However, with careful planning, collaboration, and the use of combined techniques, these challenges can be successfully overcome.

Internal network penetration testing methodology

An internal network pen test methodology is a structured approach that includes methods (what to do), techniques (how to do it), tools (what to use), procedures (an orderly sequence of execution), and objectives (what to achieve).

Various test methodologies are used to pen test internal networks, such as OSSTMM, PTES, ISSAF, MITRE ATT&CK Framework, and NIST. 

They include:

• Test methods: scanning, vulnerability exploitation, configuration analysis etc.
• Test techniques: password attacks, social engineering simulation, exploitation of specific deficiencies, e.g. Active Directory.
• Tools: Nmap, Nessus, Wireshark, Crackmapexec, Network Miner, LinPEAS/WinPEAS, ligolo, and others.

The methodology ensures the efficiency, accuracy, and repeatability of the penetration test.

So, what do we do now?

Internal network penetration testing is a critical part of any organization's cybersecurity posture. It helps identify potential deficiencies that, if exploited by harmful actors, could lead to data breaches and financial loss. These breaches would be difficult to detect without regular penetration testing.

So don't take any chances: take action now to avoid problems in the future. Contact Datami today to schedule an internal network pen test and strengthen your security. Our experts will help you find vulnerabilities and deal with all types of cyber threats.