What is Penetration Testing?
Penetration testing (also called a pen test) is a controlled security assessment where specialists attempt to access your systems in the same way a real attacker would. The goal is to find weaknesses before criminals do. The resulting report shows what was discovered, how serious each risk is, and what should be fixed first.
A pen test might examine your Microsoft 365 environment, internet-facing systems, remote access tools, cloud infrastructure, internal networks, or user privilege controls – depending on where your business is exposed.
Start With the Fundamentals before Advanced Testing
Before investing in more advanced testing, it is important to have your core security controls in place. The National Cyber Security Centre (NCSC) recommends this approach. For most UK SMEs, that means aligning with Cyber Essentials, the government-backed certification scheme designed to reduce common cyber risks.
Cyber Essentials covers five areas:
- Firewalls
- Secure configuration
- User access control
- Malware protection
- Patch management
These controls are effective because most attacks still exploit basic weaknesses: unpatched systems, weak passwords, poorly secured remote access. Fixing those fundamentals typically reduces risk faster and more cost-effectively than commissioning advanced security testing.
Once those basics are in place, some organisations move on to Cyber Essentials Plus. This is not a penetration test. It uses the same five Cyber Essentials controls, but adds an independent technical audit of in-scope systems. This includes internal and external vulnerability scanning, along with technical checks on a sample of devices and systems within scope. Others may go further still and commission penetration testing to understand how weaknesses could be exploited in practice.
When Does Penetration Testing Become Relevant for SMEs?
Common triggers for starting to look at testing include:
- Client security questionnaires asking for evidence of independent testing
- Cyber insurance renewals with stricter requirements than previous years
- Supplier due diligence checks from larger organisations in your supply chain
- Significant growth in remote working or cloud-based systems
- Handling sensitive customer data or operating in a regulated sector
A good penetration test should do more than produce a list of vulnerabilities. It should explain what was found, how it could be exploited, how serious the risk is, and what should be fixed first.
What Happens During a Penetration Test?
A penetration test is more than an automated scan. Experienced testers combine automated tools with manual investigation to identify weaknesses that automated scanning alone may miss.
A typical penetration test involves:
1. Scoping
The objectives and systems to be tested are agreed in advance. This may include internet-facing systems, cloud platforms, Microsoft 365, remote access services, or internal networks.
2. Reconnaissance
The tester gathers information about the environment in the same way a potential attacker would. This helps identify possible entry points.
3. Vulnerability Assessment
Systems are examined for known weaknesses, configuration issues, outdated software, and other security gaps.
4. Controlled Exploitation
Where appropriate, the tester attempts to exploit identified weaknesses to determine whether they could be used to gain unauthorised access, escalate privileges, or expose sensitive information.
5. Reporting and Remediation
The findings are documented in a report that explains the risks, potential business impact, and recommended actions. The focus should always be on helping organisations prioritise improvements rather than producing a long list of technical issues.
Why SME Attack Risk Has Grown
The UK Government Cyber Security Breaches Survey consistently shows that cyber attacks against small businesses are common. Most are opportunistic rather than targeted, for example criminals scanning for accessible weaknesses rather than picking a specific victim.
The most frequently exploited weaknesses are:
- Old or inactive user accounts that were never properly closed
- Missing security updates on internet-facing systems
- Exposed remote access services without adequate controls
- Weak password policies or reused credentials
- Microsoft 365 environments that have not been securely configured beyond the default settings.
As businesses add cloud services, remote access tools, and third-party platforms, there are simply more places where security weaknesses can appear.
Frequently Asked Questions
Do small businesses need penetration testing?
Not always, and not immediately. Most SMEs should first ensure that MFA, patching, endpoint protection, and Microsoft 365 security configuration are properly managed. Once those fundamentals are in place, a pen test can help answer the next question: can an attacker identify and exploit weaknesses despite those controls being in place?
Is penetration testing required for Cyber Essentials?
No. Standard Cyber Essentials certification does not require a penetration test, and neither does Cyber Essentials Plus. Some organisations choose to commission penetration testing alongside these certifications to gain additional assurance or satisfy client security requirements.
How often should SMEs carry out penetration testing?
Annual testing is common for businesses that handle sensitive information, operate internet-facing systems, or sit within larger supply chains. After significant changes to infrastructure, new cloud platforms, expanded remote access, or major system updates, earlier retesting is sensible.
Does cyber insurance require penetration testing?
Requirements vary by insurer, sector, and risk profile. Some insurers increasingly request evidence of vulnerability management, MFA deployment, and broader security assurance. If your renewal is approaching, it is worth checking the specific requirements rather than assuming last year’s documentation will still suffice.
The real value of testing
The value of penetration testing allows businesses to understand where weaknesses exist and to make informed decisions, focus investment where it matters most and improve security with confidence.