External penetration testing methodology: what is it and how does it work?

External penetration testing is a crucial cybersecurity measure that simulates real-world cyberattacks to evaluate an organisation's external defences.

By partnering with penetration testing services, businesses can identify vulnerabilities in their public-facing systems, such as web servers and network infrastructures.

This proactive approach helps organisations understand potential attack vectors and security weaknesses, offering valuable insights into how malicious actors might exploit these vulnerabilities.

What is external penetration testing?

External pentesting is often confused with another method of analysis, its counterpart, internal pentesting, which prioritises identifying vulnerabilities internal to an organisation's networks. In this instance, pentesters will simulate the behaviour of an attacker who has already managed to break in, assessing internal security flaws through this lens. Internal pentesting will cover areas such as network equipment, servers, workstations and wifi.

Contrastingly, external pentesting prioritises the identification of vulnerabilities in public-facing systems, such as web applications, networks, FTP servers, mail, routers, login systems, and sub-domains. It simulates real-world cyberattacks to evaluate an organisation's external defences, providing crucial insights into an organisation's security posture.

Why is external network penetration testing important?

External penetration testing is beneficial to organisations of any scale due to the quality of remediation advice it can provide for IT teams. Through simulating attacks, pentesting professionals can identify your organisation's security flaws, minimising the risk of exploitation via malicious attackers.

Regular testing also helps to prevent unauthorised access to networks and systems by bringing to light vulnerabilities,  allowing organisations to remediate these effectively.

External penetration testing also supports compliance with ISO 27001, the UK Data Protection Act 2018, the General Data Protection Regulation, PCI DSS, and other regulatory obligations.

When is the right time to schedule external penetration tests?

Ideally, external penetration testing should be undertaken regularly, as a proactive approach to robust cybersecurity minimises the risk of exploitation for businesses.

However, there are also specific situations where it may be particularly relevant or beneficial for your organisation to invest in an external network pentest.

For example, if your business has recently undergone significant network changes, an external pentest is always a good idea. These changes could include the addition of a third-party partner to your network, changing your cloud service provider, or changing your business's information security policies.

Additionally, it is advisable to invest in an external network penetration test if there has been a recent security incident or identified vulnerabilities. An external pentest will aid in ensuring those vulnerabilities have been sufficiently resolved, and bring to light any additional issues which may be putting your organisation at risk.

Our external network penetration testing methodology: Step by step

When conducting an external pentest for your organisation, OnSecurity will follow a structured methodology to generate effective results in an efficient and timely manner.

Our methodology is as follows:

Scoping

Firstly, we will collaborate with you to define the boundaries of the test. Clients will define the scope of their test in the online quote builder. From here, a scoping call between themselves, an OnSecurity account executive, and a penetration tester will take place to discuss the complexities of the test. Collaboratively, we will determine the networks, systems, and applications that will be targeted within the agreed scope. Access levels will also be clearly outlined.

Reconnaissance

Preliminary to the reconnaissance stage, clients will be asked to hand over their sensitive information (whitelist IP addresses, etc.) so that the test can be conducted. These prerequisites exist within the platform, with a specially designated “secrets area” for any sensitive information.

Once prerequisites have been established, our pentesters will begin to externally gather information, reconnaissance phase, digging deep into your publicly available data (DNS records, WHOIS data, etc.) in a discreet way. We'll also be using active scanning methods, such as port scanning, to identify potential vulnerabilities.

Assessment

The assessment stage is where the more hands-on testing commences, analysing the systems for weaknesses. During this phase, we'll identify vulnerabilities, assess the risk of exploitation, and conduct simulated attacks. Using a range of tools and techniques, we'll aim to validate any vulnerabilities identified, reporting on them in real-time, allowing you to remediate them effectively.

Reporting

At OnSecurity, our unique real-time reporting feature keeps clients informed with ongoing feedback throughout the test. This means that, unlike traditional pentests, the window for exploitation of vulnerabilities is far smaller. At the conclusion of testing, clients will also receive an executive summary. A detailed report will also be available to download on the platform.

Remediation

Having now identified all vulnerabilities within the external network, clients have the knowledge and resources to orchestrate remediations effectively. The remediation stage supports businesses in not only recovering from their vulnerabilities, but fortifying against them in the future.

OnSecurity offers a free retesting window for all clients to confirm remediation methods have been effective.

How external penetration testing fits into your overall security strategy

External pentesting integrates with other security practices like internal testing, cloud testing, and vulnerability management to support a robust defence system.

When reviewing your security strategy, it's important to assess how holistically you are protected: often, a combination of various testing methods can prove far more effective in protecting against the broad spectrum of online threats, fortifying your security position and minimising the risk of exploitation by malicious attackers.

External penetration testing goes beyond threat management; it is a vital part of a comprehensive cybersecurity strategy.

By focusing on external vulnerabilities, it enhances the security of public-facing business information and networks. This proactive approach strengthens defences, identifies risks, and safeguards critical assets against potential cyberattacks.

How can OnSecurity help?

Find out today how OnSecurity's external infrastructure penetration testing services can support your business in strengthening your cybersecurity posture.