What is network penetration testing and why does your business need it?

Your business network connects the people, systems, devices and data you rely on every day. It may include laptops, servers, routers, firewalls, cloud services, remote access tools, printers, Wi-Fi, Microsoft 365 and internal applications. If one weak point is exposed, it can put the wider business at risk.

Network penetration testing is a controlled security test designed to find those weaknesses before criminals do. It looks at how an attacker could try to access your systems, move through your network or reach sensitive information.

For many London businesses, this is no longer something to think about only after an incident. Network penetration testing by Northern Star can help you understand where your risks are, how serious they may be and what practical steps you should take next.

The UK Government’s Cyber Security Breaches Survey 2025/2026 found that 43% of UK businesses identified a cyber breach or attack in the previous 12 months, while phishing remained the most common type of attack, affecting 38% of businesses. That means every business needs to take network security seriously, whether you have 10 employees or several offices.

What is network penetration testing?

Network penetration testing, often called network pen testing, is an authorised test of your network security. It is carried out by security professionals who use controlled methods to identify weaknesses in your systems.

The aim is not to damage your business or disrupt your work. The aim is to show where your network could be vulnerable and how those weaknesses could be exploited.

The National Cyber Security Centre explains that penetration testing can help verify expectations about the vulnerabilities present in your systems. In simple terms, it gives you a clearer picture of whether your security controls are working as intended.

A network penetration test may look at:

External-facing systems and services
Firewalls and network boundaries
Remote access tools and VPNs
Internal network segmentation
User permissions and access controls
Weak or exposed passwords
Unpatched systems and outdated software
Misconfigured devices, servers or cloud services
Wireless networks

The test should end with a clear report that explains what was found, why it matters and what should be fixed first.

How is network penetration testing different from vulnerability scanning?

Vulnerability scanning and penetration testing are often confused, but they are not the same.

A vulnerability scan uses automated tools to identify known weaknesses, such as missing patches or insecure services. It is useful for regular monitoring and can help you spot obvious problems quickly.

A penetration test goes further. It uses manual testing, judgement and real-world attack methods to understand whether weaknesses can actually be exploited. GOV.UK’s service manual explains that vulnerability assessments help find potential weaknesses, while penetration tests proactively attack systems to find exploitable vulnerabilities.

Both approaches are useful. Vulnerability scanning helps with ongoing cyber hygiene. Penetration testing gives deeper assurance and shows what a real attacker might be able to do.

Why does your business need network penetration testing?

Your network may look safe from the outside, but hidden risks can build up over time.

Staff join and leave. Devices are added. Software is updated. Cloud services are connected. Remote working is introduced. Suppliers are given access. Over time, your IT environment can become more complex than anyone realises.

Network penetration testing helps you uncover these risks before they become expensive problems.

You may need a test if:

You have not reviewed your network security for 12 months or more
Your business has grown or changed recently
You have introduced remote or hybrid working
You rely on Microsoft 365, cloud platforms or VPN access
You handle client, financial, legal or employee data
You need to satisfy client, supplier or insurance requirements
You have experienced suspicious activity or repeated security alerts

Even if you have not had a known breach, testing can still be valuable. Many weaknesses are invisible until someone looks for them properly.

What could a network penetration test find?

A good network penetration test can uncover a wide range of issues. Some may be technical. Others may relate to process, configuration or access control.

Common findings include:

Unpatched servers or devices
Exposed services that should not be visible online
Weak password policies
Misconfigured firewalls
Old user accounts that remain active
Overly broad admin permissions
Insecure remote access settings
Poor separation between network areas
Default settings on devices
Unsupported software or operating systems

The important part is prioritisation. A useful report should not simply give you a long list of issues. It should explain which risks are urgent, which are moderate and which can be handled as part of wider improvement work.

How network penetration testing protects your business

Network penetration testing helps protect your business in several practical ways.

It reduces the risk of unauthorised access

If attackers can get into your network, they may be able to steal data, install malware, disrupt systems or move further into your environment. Testing helps identify routes that could allow this to happen.

It supports better decision-making

Business leaders do not need endless technical jargon. You need clear information about risk, impact and cost. A good test report helps you decide what to fix now and what to plan for later.

It helps protect client confidence

Your clients expect you to look after their data responsibly. If you work in sectors such as finance, legal, property, healthcare, professional services or technology, strong cyber security can also support trust during supplier reviews and tenders.

It can support cyber insurance and compliance

Some insurers, clients and frameworks may expect evidence that you are actively managing cyber risk. Penetration testing can form part of that evidence, especially when combined with vulnerability management, staff training, backups and access control reviews.

It helps prevent costly disruption

The cost of an IT security incident is not limited to the immediate repair. You may face downtime, emergency support costs, lost productivity, client complaints, reputational damage and potential regulatory consequences.

For example, if 20 employees lose 5 hours of work during an outage and the average employment cost is £30 per hour, the lost staff time alone is £3,000. That does not include missed sales, delayed projects or recovery costs.

What happens during a network penetration test?

A professional test should follow a clear process.

First, the scope is agreed. This sets out what will be tested, when the work will happen and what systems are excluded. This is important because penetration testing must be authorised and controlled.

Next, the tester gathers information about your network. They may review external services, IP addresses, domains, exposed systems and possible entry points.

The testing stage then begins. This may involve checking for known vulnerabilities, weak configurations, poor access controls and possible ways to move through the network.

After testing, you receive a report. This should include the findings, evidence, risk ratings and recommended fixes. The best reports are written for both technical teams and business decision-makers.

Finally, your business should act on the findings. This may involve patching systems, changing settings, removing old accounts, improving firewall rules, strengthening passwords or reviewing remote access.

How often should you carry out network penetration testing?

There is no single answer for every business. As a sensible starting point, many organisations consider network penetration testing annually or after significant changes.

You should also consider testing when you:

Move office or change infrastructure
Introduce a new remote access solution
Move systems to the cloud
Launch a new application or portal
Change firewall, server or network settings
Merge with another business
Need reassurance after a security incident

Penetration testing should not be treated as a one-off tick-box exercise. It works best as part of a wider cyber security plan.

Make network security part of your business planning

Network penetration testing gives you a practical way to understand your real cyber security risks. It shows where your business may be exposed, how serious the issues are and what you should do to reduce the risk.

Northern Star can help you assess your current network security, plan a controlled penetration test and turn the findings into clear, practical improvements. Whether you need support with network testing, vulnerability management, Microsoft 365 security, cyber awareness or wider IT consultancy, you can get advice that is shaped around your business.

Contact Northern Star today to discuss network penetration testing and take the next step towards a more secure, resilient IT environment.