What is Penetration Testing and How Does It Work?

Cyber threats are constantly evolving, and businesses must stay ahead of attackers to protect their sensitive data and systems. One of the most effective ways to assess security weaknesses is through penetration testing (also known as pen testing).

Penetration testing goes beyond automated scanning tools—it involves manual testing, exploitation attempts, and detailed analysis to uncover cybersecurity gaps that may be missed by traditional vulnerability scanners. In this article, we will explore penetration testing, its methodology, and the importance of choosing a highly qualified provider.

What is Penetration Testing?

Penetration testing is a controlled security assessment where ethical hackers simulate real-world cyberattacks on a company’s IT infrastructure, web applications, or internal systems. The goal is to identify vulnerabilities before malicious hackers exploit them.

A penetration test involves a combination of automated tools (such as vulnerability scanners) and manual techniques to uncover security flaws. The human element in penetration testing is critical, as skilled ethical hackers can find complex attack chains that automated tools often miss.

Types of Penetration Testing 

Different businesses have different security needs. Here are the main types of penetration testing: 

Network Penetration Testing 

• Assesses vulnerabilities in an organisation’s internal and external networks. 

• Tests for misconfigurations, open ports, outdated protocols, and weak credentials. 

Web Application Penetration Testing 

• Evaluates web applications for common threats like SQL injection, XSS (Cross-Site Scripting), CSRF (Cross-Site Request Forgery), and authentication bypass. 

• Ensures security best practices are followed in web development. 

Cloud Penetration Testing 

• Focuses on cloud environments such as AWS, Azure, and Google Cloud. 

• Identifies misconfigurations, improper access controls, and weak API security. 

External Penetration Testing 

• Simulates attacks on public-facing infrastructure such as web servers, email systems, and VPNs. 

• External pen testing identifies vulnerabilities that could be exploited by external attackers to gain access to internal systems. 

• Assesses firewall configurations, exposed services, and misconfigurations that could lead to a security breach 

Physical Penetration Testing 

• Assesses physical security by attempting unauthorised access to buildings, server rooms, and sensitive areas. 

• Tests security controls like badge access, CCTV monitoring, and response protocols. 

Wireless Penetration Testing

• Wireless penetration testing focuses on Wi-Fi networks, Bluetooth, and other wireless technologies to detect unauthorised access points and weak encryption. 

 

What are the 7 Steps of Pen Testing? 

A penetration test follows a structured methodology to ensure a thorough security assessment. The key phases include: 

1. 
   

   Planning and Scoping

Before starting the test, the penetration tester or cyber professional works with the client to define: 

• The scope (e.g., web apps, networks, or cloud services). 

• The testing goals (e.g., identify exploitable vulnerabilities). 

• The rules of engagement (to ensure no business disruption). 

2. 
   

   Reconnaissance and Information Gathering

The ethical hacker collects public and private data about the target to identify potential attack vectors. This includes: 

• Open-source intelligence (OSINT). 

• Identifying exposed credentials, IP addresses, and misconfigurations. 

• Gathering employee information for social engineering attacks. 

3. 
   

   Scanning and Enumeration

• Using tools like Nmap, Nessus, and OpenVAS, the tester scans for open ports, services, and vulnerabilities. 

• Identifies weak authentication mechanisms, outdated software, and misconfigurations. 

4. 
   

   Exploitation (Attacking the System)

This phase involves actively trying to exploit vulnerabilities found during scanning. Common techniques include: 

• Brute force attacks (guessing weak passwords). 

• SQL injection (to access sensitive databases). 

• Privilege escalation (gaining higher-level access). 

• Pivoting (moving from one compromised system to another). 

5. 
   

   Post-Exploitation and Persistence

After gaining access, the tester evaluates: 

• How deep they can go into the system. 

• Whether they can exfiltrate sensitive data. 

• If they can maintain access without being detected. 

6. 
   

   Reporting and Recommendations

• A detailed report is provided, outlining:  

• The vulnerabilities discovered. 

• How they were exploited. 

• Risk levels and potential business impact. 

• Actionable recommendations for fixing security issues. 

7. 
   

   Retesting (Optional)

Once the company fixes the vulnerabilities, a retest is done to verify if the security gaps have been successfully patched. 

Real-World Example: What Automated Scanners Missed 

During a web application penetration test we conducted for a client, our manual testing approach uncovered a critical security flaw that vulnerability scanners had completely missed. 

• The web application was hosted on a public-facing server but had a direct connection to the client’s on-premises SQL server. 

• Due to lack of proper network segmentation, we were able to move laterally from the web server to other internal servers and services. 

• This exposed sensitive customer data, financial records, and privileged access credentials. 

Had an attacker discovered this flaw, they could have gained full control over internal systems. This issue highlights why manual penetration testing is crucial—automated vulnerability scanners would have never identified the risk! 

The Role of Kali Linux Tools in Penetration Testing 

Kali Linux is the go-to penetration testing operating system, widely used by security professionals. It includes hundreds of pre-installed security tools for: 

• Network scanning (Nmap, Netdiscover) 

• Web application testing (Burp Suite, OWASP ZAP) 

• Password cracking (John the Ripper, Hashcat) 

• Exploitation (Metasploit, SQLmap) 

• Wireless testing (Aircrack-ng, Wireshark) 

Kali Linux provides everything an ethical hacker needs to conduct a thorough penetration test and identify real-world attack vectors. 

Choosing the Right Penetration Testing Provider 

When selecting a penetration test provider, it’s essential to verify their credentials. Look for testers who hold industry-recognised certifications, such as: 

✅ Cyber Scheme Certified Tester (CSTM/CTL) – A NCSC accredited standard for penetration testing competency.
✅ CREST Registered Tester (CRT/CCT) – A NCSC accredited standard for penetration testing competency.
✅ UK Cyber Security Council Registration – A step up, indicating adherence to the highest industry standards. 

A certified penetration tester helps ensures quality, professionalism. 

Why is Penetration Testing Important? 

Penetration testing is not just a compliance requirement – it is a proactive way to protect your business. Here’s why it matters: 

✅ Identifies Security Gaps – Uncovers unknown vulnerabilities before hackers do.
✅ Prevents Data Breaches – Helps businesses avoid financial and reputational damage.
✅ Ensures Compliance – Meets security standards like ISO 27001 or any contractual obligations you have.
✅ Tests Incident Response – Evaluates how well your security team can detect and respond to threats.
✅ Builds Customer Trust – Shows clients and stakeholders that security is a priority. 

Penetration testing is an essential cybersecurity practice that helps businesses stay ahead of cyber threats. By simulating real-world attacks, organisations can identify vulnerabilities, strengthen security defences, and prevent costly breaches. 

If you’re looking for expert penetration testing services, Resolute Cyber provides CREST-accredited security assessments tailored to your business needs. 

Contact us today to begin your journey!