Everything you need to know about penetration testing

Penetration testing, also known as pen testing or ethical hacking, is the practice of attacking a computer system or network to uncover security vulnerabilities. These vulnerabilities can then be fixed before an attacker exploits them. Pen testers use a variety of methods in their attempts to penetrate systems, such as exploiting known vulnerabilities or guessing passwords.
30.06.23 AAG Digital
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Why penetration testing is important

Pen tests provide valuable insights into a business’s security measures’ effectiveness. By attempting to gain access to your systems in a controlled environment, you can patch detected vulnerabilities before they are exploited.

Therefore, penetration testing is critical to any robust cyber security strategy. It is important to note that penetration testing should be conducted by qualified and experienced individuals, as it can potentially introduce new vulnerabilities if not done correctly.

When to conduct a penetration test?

Cyber attacks constantly evolve, so penetration testing should ensure your business stays abreast of the latest threats. Any significant infrastructure changes, such as deploying new operating systems, should be accompanied by a penetration test to highlight potential risks within your network architecture.

Furthermore, if you suspect that your network has been compromised, you should conduct a penetration test as soon as possible to determine the extent of the breach and take steps to mitigate the damage.

Types of penetration test

External penetration test:

An external penetration test focuses on gaining access to systems and data from outside the network perimeter. This type of test is typically used to simulate an attacker who has no inside knowledge of the network. External pen tests are useful for exposing issues with a business’ cyber security, such as faulty access points or misconfigured firewalls.

Internal penetration test:

Internal penetration testing is a type of ethical hacking in which the tester acts as a malicious party who is familiar with a company’s systems and networks. This simulates either an external hacker who has already managed to penetrate the network and seeks to escalate privileges or an internal administrator looking to cause damage. These tests are useful for identifying what data would be at risk should a hacker gain access to a company’s IT infrastructure.

Network Penetration Testing

Network penetration testing is the process of identifying security vulnerabilities in the network infrastructure of a business. This involves grading the security capabilities of wired infrastructure, such as servers and workstations. The wired network is particularly susceptible to distributed denial of service (DDoS) attacks and malware.

Wireless network

Wireless network penetration testing is the process of identifying security vulnerabilities in wireless network infrastructure. This involves grading the security capabilities of wireless devices, such as laptops and public and private Wi-Fi networks. For instance, poorly configured Wi-Fi networks may allow a malicious actor to connect to the public network and access information normally hidden in a private network.

Web application

Web applications are increasingly used to handle sensitive data and are critical for effective business operations. Web app security testing helps expose any application vulnerabilities, from the code to the user interface. The top web application security risks are:

Broken access controls: Access controls ensure users cannot act outside of their permissions. Failure of these controls can lead to unauthorised access to sensitive data.

Cryptographic failures: This covers a broad range of issues with data encryption in storage and transmission. Unsecured data is easier to access and expose.

Injection:  A vulnerability where user input is incorrectly handled and used to execute unintended actions. This can allow an attacker access to sensitive data or control of the web application.

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Penetration testing methodology

Black box penetration testing

In a black box pen test, the tester has no prior knowledge of the network or systems.

The pen tester takes the role of an unprivileged external attacker, using penetration testing tools to attempt to breach a network. This scenario is the most authentic of any penetration test, demonstrating how a malicious actor with no inside knowledge would target and compromise a business.



  • Depending on the scope, black box pen testing can include all aspects of a business’ IT infrastructure.
  • Provides a realistic security review.


  • May be less targeted than a white box test.
  • Can take longer to complete than other methodologies.

White box penetration testing

White box penetration testing involves sharing full network and system information with the tester, including network maps and credentials. A white box test is best employed to test the security of specific systems or applications using as many attack vectors as possible.

As the tester has complete knowledge of the network and systems design, a white box test offers a high degree of accuracy in identifying vulnerabilities. This allows for a more comprehensive assessment of your security posture and identifying vulnerabilities that may be missed in a black box test.


  • Greater accuracy in identifying vulnerabilities than black box testing
  • Usually quicker to compete than black box testing


  • Particularly complex systems may take a long time to be thoroughly tested
  • Vulnerabilities could be missed as only the disclosed information is tested.


Grey box penetration testing

Grey box testing is a mix of black and white box testing, where the security company has some knowledge of the network but not all. This gives the pen tester enough information to prioritise testing, and focus on the most vulnerable parts of the system.


  • Testers can focus on specific areas
  • Can be completed in a shorter time frame than a full black box test


  • May not be as comprehensive as a full black box test
  • Testers may need more time to familiarise themselves with the systems than in a white box test.
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The benefits of penetration testing

Identifying security vulnerabilities

Penetration testing is an effective way to identify security vulnerabilities in a system. By simulating real-world attacks, testers can identify areas that are susceptible to abuse and exploitation. Vulnerabilities can then be fixed before an attacker has a chance to exploit them.

Improved security posture

Penetration testing can also help to improve the security posture of an organisation. By identifying and fixing vulnerabilities, organisations can make it more difficult for attackers to successfully compromise their systems. In addition, penetration testing can help organisations to develop better security policies and procedures.

Demonstrating compliance

Businesses that are subject to industry or government regulations may need to demonstrate compliance. Penetration testing can help to do this by providing evidence that a system is secure and that any vulnerabilities have been identified and addressed.

Improve your security awareness

Penetration tests can highlight where your employees may be vulnerable to social engineering attacks. Training your staff on online dangers helps keep your data safe.

Reduce false positives

Penetration testing can help reduce the number of false positives generated by security tools such as intrusion detection systems (IDS) and vulnerability scanners. By identifying which alerts are genuine threats and which are not, businesses can focus their efforts on the most serious incidents.


Potential risks of penetration testing

Penetration testing is an important part of any security strategy, but it’s not without its risks. Make sure you understand the potential risks involved before conducting any tests.

Inadvertently cause system outages or data loss

If systems are not configured correctly, penetration testing can cause unexpected outages. Testers should have experience in administering the systems they are testing and understand the risks involved.

Security breaches

In some cases, penetration testers may inadvertently breach security protocols. This is more likely to occur in black box testing, as the tester has no prior knowledge of the system.

Damage to equipment

In rare cases, penetration testing may damage equipment if conducted without proper care. Testers should be well-versed in the tools and techniques they are using to avoid any accidental damage.

Inaccurate findings

If tests are not conducted properly, the results may be inaccurate. This could lead to a false sense of security if vulnerabilities are not identified, or unnecessary panic if false positives are reported.

Can be time-consuming

Depending on the scope of the engagement, penetration testing can take a long time to complete, especially if there are restrictions on when the tests can take place. For instance, restricting testing to outside business hours can prolong the engagement.

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The stages of a penetration test


Before testing begins, the scope is defined. This means excluding any systems and highlighting any areas of particular focus. Based on the scope and when testing can take place, a timeframe is established so all parties understand what will happen and when.

Reconnaissance and scanning

The first stage of a penetration test involves the tester scanning the network to identify any weaknesses. This includes vulnerabilities such as open ports, poorly configured password policies and unpatched software.

Exploiting vulnerabilities

The tester will then attempt to exploit any vulnerabilities they have found.

Escalating privileges

Once the tester has gained a foothold with the network, they will then attempt to escalate their privileges. This usually involves gaining access to central databases and critical systems. It’s important to note that this is done in a controlled environment, so no data is stolen or systems compromised.

Ending engagement and reporting

Once testing is complete, the network is returned to its original state and the tester generates a report with their findings. This allows the business to make any necessary changes to their security before vulnerabilities can be exploited.

One of the best defences against cyber threats

Cybersecurity is an important issue for any business, and penetration testing is one of the best ways to find out where your vulnerabilities lie.

While it can be expensive and time-consuming, the findings are invaluable to understanding your company’s vulnerabilities in order to protect against security breaches. A good penetration tester will create an accurate report of their findings after conducting a penetration test for you to use as a roadmap going forward.

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