Network Penetration Testing: A Comprehensive Guide

What is a Network Penetration Test?

A network penetration test is a type of penetration test, or pentest, in which a pentest expert or ethical hacker attempts to identify vulnerabilities in an organisation’s network infrastructure using internal and external network tests. 

During a network penetration test, a pentester will test network devices, such as routers and firewalls, servers and workstations, and wireless networks, and grade the severity of the vulnerability so that they can report their findings and offer remediation advice.

Why are Network Penetration Tests Important?

Network penetration tests are extremely important regardless of company size because they help to identify and remediate cybersecurity vulnerabilities before they can be exploited. 

By taking a proactive approach to cybersecurity, an organisation can significantly reduce the risk of falling victim to a cyber attack, protect sensitive data, ensure compliance with regulatory standards, and safeguard assets and reputation.  

Types of Network Penetration Testing

As with any penetration test, there is no one-size-fits-all approach to network penetration testing. The type of test depends entirely on what you’re testing and how in-depth you want it to be. So, here are a few of the most common types of network penetration tests.

External Testing

In network penetration testing, external testing involves analysing and identifying vulnerabilities in an organisation’s outward-facing infrastructure, such as web servers, email servers, and firewalls, from outside the network. 

Internal Testing

In network penetration testing, internal testing involves assessing and identifying vulnerabilities in an organisation’s internal infrastructure, such as workstations and internal applications. Internal testing aims to identify vulnerabilities that can be exploited by insiders or attackers who have already breached the external perimeter digitally or physically. 

Black Box or Blind Testing

Blind testing involves assessing the security of an organisation’s network, with the pentester having minimal prior knowledge of the network infrastructure. It is supposed to simulate an external attacker’s approach to identifying vulnerabilities and weaknesses based solely on what can be observed and discovered during the test.

Red Teaming or Double-Blind Testing

In double-blind testing, neither the pentesters nor the organisation’s IT staff are aware of the specifics of the test. Double-blind tests are supposed to simulate a real-world attack scenario, ensuring unbiased results, an accurate measure of vulnerability severity, and an organisation’s incident response and detection capabilities.

Purple Teaming or Targeted Testing

In targeted testing, the pentesters and the organisation’s IT staff are aware of the test and collaborate closely. This approach focuses on specific systems and areas of concern, allowing for a more efficient and thorough assessment of known critical assets and vulnerabilities. 

Phases of Network Penetration Testing

Like vulnerability assessments and penetration tests, network penetration tests are divided into five phases: planning and reconnaissance, scanning and enumeration, exploitation, post-exploitation, and reporting. 

Planning and Reconnaissance

In this stage, the pentester gathers information about the target network and identifies potential vulnerabilities through passive and active reconnaissance. Passive recon collects information without directly interacting with the target, while active recon gathers information through interaction.

Scanning and Enumeration

In this stage, the pentester uses automated tools to identify open ports, services and devices on the network. The pentester then uses all of this to extract detailed information about the network and its resources, such as user accounts, network shares, and running services. 

Exploitation

Here, the pentester will attempt to exploit identified vulnerabilities to gain unauthorised access or control over network resources. 

Post-Exploitation

Here, the pentester will develop an impact assessment that determines the potential impact of the successful exploit. This will be done by analysing what systems can be controlled, what data can be accessed, whether they can maintain access using backdoors or by creating new user accounts, and whether they can move laterally through the system to gather more data. 

Reporting and Remediation

Once they have completed the network penetration test, the pentester will document their findings, analyse the overall security posture of the network, and report their findings along with remediation advice for patching vulnerabilities. 

What Tools and Techniques are Used in Network Penetration Testing?

Like all types of penetration tests, there are far too many individual tools to list, and the right tool for the job can sometimes come down to a matter of personal preference. So, here are a couple of tools we use when conducting network penetration tests.

Nmap – Network Scanning

“Nmap, also known as Network Mapper, is a highly effective and adaptable network scanning tool. With Nmap, users can effortlessly discover hosts and services on a computer network, detect operating systems, identify open ports, and collect information about different network devices.”

There are 65,535 possible ports on an IP address, and checking all of them manually takes a very long time. So, pentesting companies often use active scanning tools, such as Nmap, to find open ports before cataloguing them depending on what sort of traffic they receive and transmit and what versions they are running, i.e., whether they’re up-to-date. 

Nessus Expert – Vulnerability Scanning

“Nessus Expert is an effective tool to help you discover vulnerabilities across your attack surface. It supports scanning across a variety of asset types such as operating systems (MacOS, Windows, Linux), applications, network devices and more.”

Similar to Nmap, tools like Nessus can scan entire networks or work in tandem with tools like Nmap to scan specific ports. Using its database of known vulnerabilities, it can highlight specific vulnerabilities within the network. 

Other vulnerability scanners commonly used by pentesting companies include Qualys and Nexpose.

What are the Benefits of Network Penetration Testing?

There are too many benefits of network penetration testing to list them all, so we’ve picked three of the most important ones.

Identifying and Remediating Network Vulnerabilities

The most obvious benefit is that network penetration tests highlight vulnerabilities in your internal and external network infrastructure. Once the vulnerabilities have been identified, they can be remediated before attackers can exploit them. 

Compliance

Regular network penetration tests can help your organisation meet regulatory and industry standards, avoid penalties, and ensure data protection. Non-compliance is significantly more expensive than compliance. 

Maintain Trust

Cyberattacks can be extremely damaging to your brand reputation, so preventative action helps maintain brand trust. Few things can take down established organisations quite like client or employee data breaches. 

Common Misconceptions of Network Penetration Testing?

Network penetration testing is complicated, so it’s unsurprising that there are an abundance of misconceptions. 

Pentesters Do Not Fix the Vulnerabilities

We’ve spoken about this before in our “Comprehensive Guide to Penetration Testing”, but the same is true here. The job of the pentester is to identify vulnerabilities, attempt to exploit them to judge the severity of the vulnerabilities, and report them and offer remediation advice. It is not the pentesters’ job to fix the vulnerabilities they identify.

Fixing vulnerabilities is a completely different service and is best carried out by expert developers and IT specialists. Most companies have their own in-house developers who can do this, but if you do not, hiring pentesters to fix vulnerabilities is significantly more time-consuming and expensive than hiring most third-party developers.

We Should Only Focus On Our External Network Infrastructure

Protecting your external network infrastructure is obviously extremely important, but many organisations focus on it so much that they neglect their internal infrastructure. Organisations that do this usually say, “If we can stop people getting in, why do we need to worry about the inside?” 

This line of thinking has two major flaws. Firstly, if someone does manage to penetrate your external infrastructure, perhaps by exploiting a new vulnerability or one that no one had found previously, they now have full control of your network. This is very much an all-eggs-in-one-basket approach. 

Secondly, the attack may come from the inside. If an attacker is able to gain internal access using employee credentials or by physically breaking into an organisation’s office, little to nothing will stop them from carrying out their attack.

For any history fans, think of Troy and Constantinople. Troy fell because deception and human error enabled the Greeks to bypass the external infrastructure. Constantinople fell because technological advancement in the form of cannons rendered the city’s two stone walls obsolete. In both cases, dependence on their external infrastructure was their undoing. 

Network Penetration Tests Are Only For Large Enterprises

It is dangerous to assume that any form of penetration testing, let alone network penetration testing, is exclusively for larger organisations. While these tests can be expensive, cyberattacks can affect any company, regardless of size. In fact, many attackers actively target smaller organisations because they often lack the cybersecurity capabilities to deter them.

If funding is holding you back, there are things you can do to remain secure. For example, if you have to get an annual pentest for compliance reasons, there’s no point testing the same things year after year. One year, test your external network; the next year your internal network, and so on and so forth. 

Tackling your cybersecurity bit by bit is always going to prove more fruitful than not looking at it at all.

Conclusion

A network penetration test is a type of penetration test, or pentest, in which a pentest expert or ethical hacker attempts to identify vulnerabilities in an organisation’s network infrastructure using internal and external network tests.

External network penetration tests are the most common form of network pentest; however, internal pentests are equally as important and should not be neglected.

Network penetration tests should be carried out as often as possible, or annually, at a minimum.

Regardless of the size of your organisation, network penetration tests are important and should be carried out to ensure you avoid being the target of a cyberattack, which could cause irreparable damage to your organisation.