Network Penetration Testing: Definition, Types, Process, Tools, and Cost

Network penetration testing is a security assessment that simulates real-world cyberattacks to identify vulnerabilities, misconfigurations and weak points inside the organisation’s network infrastructure. Network penetration testing has two major types: external network penetration testing and internal network penetration testing.

The process of performing network penetration testing begins with defining the network penetration testing scope and ends with a final retest to verify that all discovered vulnerabilities have been properly fixed. Penetration testers use a range of specialised tools such as scanners, enumeration utilities and exploitation frameworks. These tools help them to find security gaps across devices, servers, firewalls and network services.

The cost of performing network pentesting depends on network size, complexity and the required depth of the testing, but on average it is around £2,500 to £15,000. Hiring a professional network penetration testing service is often the safest approach, considering the increasing number of cyberattacks.

According to M. Alhamed et al in their research, A Systematic Literature Review on Penetration Testing in Networks: Future Research Directions, published on June 9, 2023, automated network penetration testing using machine learning in WLAN testing is recommended for improving security, supporting future research and reducing potential losses.

What is network penetration testing?

Network penetration testing is an ethical simulation of cyberattacks on an organisation’s network infrastructure to identify and address security vulnerabilities before malicious attackers can exploit them. Network penetration testing is also known as infrastructure penetration testing.

Network penetration testing (pentesting) began as a proactive, manual approach to simulate cyberattacks and identify security vulnerabilities in computer networks and systems. Earlier in the 1960s, penetration testing methods relied on the expertise of security professionals, who used real attackers’ techniques to uncover weaknesses before malicious actors could exploit them. Over time in the 2000s, the network penetration testing process evolved with structured methodologies and processes such as planning, information gathering, vulnerability detection, exploitation and reporting and became a recognised component of cybersecurity audits.

How does network penetration testing work?

Network penetration testing involves simulating real-world attacks on an organisation’s network infrastructure to identify and address vulnerabilities in a network. Ethical hackers use a structured approach that includes planning, information gathering (Reconnaissance), vulnerability analysis, exploitation, privilege escalation & lateral movement, post-exploitation and reporting.

Penetration testers use a combination of automated scanners and manual testing to discover vulnerabilities like open ports, exposed services, weak or misconfigured firewalls, unpatched vulnerabilities, weak authentication mechanisms, poor network segmentation, insecure VPN or remote access configurations and misconfigured cloud or hybrid network components.

The primary goal of network penetration testing is to discover and fix vulnerabilities in the network before malicious attackers can exploit them. M. Alhamed et al state in their research, ‘A Systematic Literature Review on Penetration Testing in Networks: Future Research Directions,’ published on June 9, 2023, that Network penetration testing is a security assessment that finds risk areas and vulnerabilities that threaten the security of a network, providing prevention and detection controls against attacks in the network.

What are the two types of Network penetration testing?

The two types of network penetration testing are Internal Network penetration testing and External Network penetration testing.

1. Internal Network Penetration Testing

Internal network penetration testing involves simulating attacks from within an organisation’s network, such as those by employees or attackers who have already gained initial access to the network. The goal of internal network penetration testing is to evaluate the potential impact and damage an internal threat actor could cause, including privilege escalation and lateral movement within the network.

Internal network penetration testing process involves connecting directly to the internal network through on-site access, a simulated compromised workstation or VPN access. Pen testers scan for open ports, identify outdated or vulnerable systems, map internal hosts, attempt privilege escalation and check weak segmentation between departments. For example, an internal network pentest may find that an attacker who compromises an employee’s laptop can move freely into the finance server due to poor network segmentation or weak admin credentials.

Internal network penetration testing also evaluates Active Directory security, including domain controller configurations, Group Policy Objects (GPOs), Kerberos authentication weaknesses, service account permissions, trust relationships between domains and privilege escalation paths that could allow an attacker to gain domain administrator access.

2. External Network Penetration Testing

External network penetration testing involves simulating an attack from outside the organisation’s network, attempting to breach the network perimeter. The goal of external network penetration testing is to identify weaknesses in internet-facing systems such as firewalls, web servers, VPN portals, DNS and email services that malicious attackers could exploit to gain initial access.

External network pentesting is conducted by scanning public IP ranges, enumerating exposed services, identifying vulnerabilities and attempting exploitation without any internal access. Ethical hackers try to access through firewalls, exploit unpatched services, bypass authentication, or misuse misconfigured cloud and web services. For example, an external penetration test may identify an outdated VPN gateway vulnerable to remote code execution that allows an attacker to gain initial access to the organisation’s network from the internet.

What are the steps to perform network penetration tesing?

The 11 steps to performing network penetration testing are explained below.

1. Define the Network Pentesting scope and engagement parameters

Defining the network pentesting scope and engagement parameters involves identifying in-scope IP ranges, timelines, testing limitations, objectives and required permissions. Defining scope and engagement includes reviewing network diagrams, understanding business goals and agreeing on report requirements. The main input of this process is organisational information, and the output is a signed scope and rules-of-engagement document that legally authorises the test.

2. Conduct passive reconnaissance intelligence gathering

Conducting passive reconnaissance means gathering information about the target network without directly interacting with it, which helps avoid detection. Passive reconnaissance includes checking DNS records, leaked credentials, domain metadata and public asset information. Tools like Shodan, Whois, Censys and DNSdumpster are used for passive reconnaissance. The output of this process involves an intelligence profile that outlines the external attack surface and clues about potential vulnerabilities.

3. Perform active network discovery scanning

Performing active network discovery scanning is about where you start interacting with the network to identify reachable systems. Pen testers use tools like Nmap, Masscan and ARP-scan to perform ping sweeps, ARP discovery and TCP/UDP ports scans and find live hosts and open services. Input of this active scanning includes IP ranges defined in the scope, while the output is a complete list of active devices and exposed entry points.

4. Enumerate services and network topology

In enumerating services and network topology, pen testers gather deeper information about each identified service, including version numbers, SNMP information, OS fingerprints, SMB shares and user accounts. This process helps map the internal network topology and trust relationships. Pen testers commonly use tools like Nmap, NSE scripts, SMBclient, Netcat and SNMPwalk. The output of this process includes a detailed network and service profile showing how systems communicate and where weaknesses are.

5. Analyse vulnerabilities using automated scanners

Automated scanners are used to analyse the discovered services for known flaws, insecure configurations, outdated software and weak protocols. Pen testers use tools like Nessus, Qualys, and OpenVAS, which help generate vulnerability reports. It is important to consider that automated results often contain false positives, so manual verification is needed. The output of automated scanners is a severity-based vulnerability list.

6. Exploit identified network security weaknesses

Exploiting identified network security weaknesses involves ethically exploiting vulnerabilities once they are validated to prove their impact. Pen testers use tools like Metasploit, Hydra and custom scripts to safely attempt to exploit vulnerable services like weak passwords, outdated servers or exposed administrative services. The output is proof-of-concept access to demonstrate real-world risk.

7. Escalate privileges within compromised systems

Escalating privileges within compromised systems involves attempting to elevate your privileges to administrators or root to expand control after gaining initial access. This involves exploiting local misconfigurations, weak permissions or vulnerable kernel components using tools like LinPEAS, WinPEAS and Metasploit modules. The output is privileged access, enabling deeper testing in a controlled manner to avoid destabilising systems.

8. Perform lateral movement across the network

Performing lateral movement across the network is about assessing how far an attacker can go inside the network once one system is compromised. Pen testers use tools like PsExec, CrackMapExec, SSH pivoting, or RDP relays to move between devices based on trust relationships, exposed internal services or reused credentials. The output is a map of pivot paths and possible attack routes across the network.

9. Exfiltrate sensitive data or assets

Controlled data access verification is performed by demonstrating reachability to sensitive data or critical assets without extracting production information. Pen testers document proof of access, such as directory listings, file metadata or sanitised screenshots, to demonstrate the real impact of compromise. Only pre-approved test data is accessed or transferred to maintain safety and compliance.

10. Document findings with remediation recommendations

Documenting findings with remediation recommendations includes compiling all observations, exploited vulnerabilities, impact analysis, evidence and remediation suggestions into a clear network penetration testing report. The network penetration test report includes technical details for IT teams and executive summaries for leadership. The output is a professional report that helps the organisation improve its security posture.

11. Retest after vulnerability patch implementation

Restesting after vulnerability patch implementation is about applying fixes to confirm all vulnerabilities have been successfully patched. Pen testers use tools like Nmap, Nessus and manual exploitation attempts to validate remediation. The output is a retest report that verifies fixes and ensures no residual issues remain.

What tools are used to perform network penetration testing?

Network penetration testing tools are used by ethical hackers to scan, analyse, exploit and assess security weaknesses within the network. Network pen testing tools help find open ports, detect vulnerabilities, map network services, exploit misconfigurations and evaluate how an attacker might gain unauthorised access.

The top 10 network penetration testing tools are described below.

• Nmap: Nmap or Network Mapper is a free and open-source network scanning tool which is used to identify open ports, active hosts and running services. Pen testers use Nmap to map the structure of a network and uncover exposed entry points. Pen testers use Nmap in network pentesting for reconnaissance, service enumeration and vulnerability identification before the exploitation begins.
• Nessus: Nessus is a vulnerability scanner that finds security flaws such as misconfigurations, missing patches, weak protocols and outdated software. Nessus is not an open-source tool, but it provides a free, limited version (Nessus Essentials). Pentesters use Nessus in network pentesting to perform automated vulnerability assessment across internal and external network assets.
• Metasploit: Metasploit is an open-source exploitation framework that provides tools, payloads and modules for conducting controlled attacks on systems. Metasploit helps pentesters validate vulnerabilities by attempting real-world exploitation. In network pentesting, Metasploit is used to exploit weak services, escalate privileges and check the effectiveness of network defences.
• BloodHound: BloodHound is a free, open-source Active Directory reconnaissance tool that maps attack paths and privilege escalation routes within Windows domains. Pen testers use BloodHound in internal network pentesting to visualise how an attacker could escalate from a standard user account to a domain administrator.
• Wireshark: Wireshark is a free and open-source network protocol analyser that is used in network pentesting to capture and inspect network traffic. Wireshark helps find insecure communication, suspicious packets, plaintext credentials and protocol-level weaknesses. Pentesters use Wireshark to analyse network behaviour and identify vulnerabilities in data transmission.
• Burp Suite: Burp Suite is a web security testing platform that is used to analyse and exploit vulnerabilities in web applications within the network. Burp Suite is not fully open-source; it provides a free Community edition. Burp Suite is used in network pentesting to test web interfaces, authentication flows, API endpoints and traffic manipulation.
• Hydra: Hydra is a free, open-source brute force tool that is used in network pentesting to perform credential attacks against network services like SSH, FTP, Telnet, SMB and HTTP logins. Hydra help pentesters identify weak or default credentials that could allow attackers to gain an initial foothold into network systems.
• OpenVAS: OpenVAS is a free and open-source vulnerability scanning tool similar to Nessus. OpenVAS is used in network pentesting to scan servers and network devices for misconfigurations, weak encryption, outdated services and other vulnerabilities. OpenVAS helps perform comprehensive security assessments across internal networks.
• Aircrack-ng: Aircrack-ng is a free and open-source toolkit that is used to assess the security of wireless networks. Aircrack-ng helps capture Wi-Fi packets, cracks WPA/WPA2 keys and checks for weak encryption. Aircrack is used in network pentesting to evaluate Wi-Fi security, rogue access points and wireless attack risks.
• Nikto: Nikto is a free and open-source web server vulnerability scanner that checks for insecure files, outdated software, misconfigurations and dangerous scripts. Nikto is used in network pentesting to identify weaknesses in web servers exposed on the network perimeter.
• John the Ripper: John the Ripper is a free and open-source password-cracking tool used to test password strength by analysing hashed passwords. John the Ripper is used in network pentesting after gaining access to cracked password hashes from servers or network devices to identify weak password policies.

Nmap is widely considered the most essential among network penetration testing tools because it is versatile, extensively documented and commonly used for scanning, discovery and enumeration across the industry.

How much does it cost to perform network penetration testing?

The cost of performing network penetration testing ranges from £2,500 to £15,000+. The factors affecting the cost of network pentesting include scope, complexity, provider and methods used.

For an SMB organisation, a basic external network test can cost about £2,500, and internal network tests may cost around £4,000. According to a public-sector G-Cloud rate sheet network (external or internal), the testing cost day rate per consultant is £750/day. For very large, complex or “red team” style assessments, cost can go £20,000+; some red teaming or full-spectrum engagements may reach £50,000+ according to some providers.

UK service providers charge £100-£300 per hour for experienced penetration testers. Depending on the tester’s expertise and the complexity of the network, the daily rates for performing network pentesting range from £750 to £2,500 per day. The weekly rates for comprehensive assessments cost £3,000–£10,000+ per week, and for ongoing or large-scale engagements, the assessment costs £15,000–£40,000+ per month.

Can you perform network penetration testing on your own network?

Yes, you can perform network penetration testing on your own network as long as you have proper authorisation and follow ethical guidelines.

Local network penetration testing, also called internal penetration testing, is a security assessment performed inside your own internal network to evaluate the security from the perspective of an insider, such as an employee or someone with physical or logical access to the internal LAN (Local Area Network).

Performing local network pentesting requires a properly configured testing machine with tools such as Nmap, Wireshark, Metasploit, Hydra and vulnerability scanners. You begin by connecting to your own local network (through Ethernet or Wi-Fi) and mapping all active devices, exposed services and open ports using scanners.

The next step involves enumerating systems to identify misconfigured routers, outdated software, insecure SMB shares, weak firewall rules or default credentials. You attempt safe exploitation to validate risks after discovering vulnerabilities, such as cracking weak passwords, testing privilege escalation, or checking if lateral movement is possible between devices.

Record findings, evidence and assess how an attacker might reach sensitive resources like admin consoles, IoT devices or NAS storage throughout the process. Finally, create a remediation plan and fix issues by patching systems, enabling segmentation, strengthening passwords, disabling unused services and tightening firewall rules.

What are the factors affecting the cost of network penetration testing?

The main factors affecting the cost of network penetration testing are described below.

1. Size of the network: The cost of network penetration testing is directly affected by the number of IP addresses, routers, servers, switches, cloud resources and endpoints. A larger network requires more analysis, scanning and manual testing, which increases overall cost.
2. Complexity of the infrastructure: Complex environments such as legacy systems, hybrid cloud networks, multi-site networks, VPN gateways and custom protocols require more effort and specialist skills. The more complex the infrastructure, the higher the network penetration testing cost.
3. Scope of Testing (Internal vs. External): External testing typically has a limited scope and focuses on internet-facing systems, whereas internal testing assesses a broader range of devices once they are inside the network. Larger or more detailed scopes significantly increase the cost.
4. Tester experience & certifications: Penetration testers with highly qualified skills (CREST, CHECK, OSCP, SC-cleared, senior consultants) charge higher day rates. They charge higher because they have more experience in network penetration testing.
5. Time requirement & duration of engagement: Longer projects naturally increase cost. Testing time depends on the number of systems, vulnerabilities discovered, and how much manual exploitation is required.
6. Compliance requirements: Testing done for regulations like UK GDPR, ISO 27001, PCI DSS, Cyber Essentials or SOC 2 requires additional documentation, evidence collection and specialised reporting, which increases the cost.

How can Cyphere help you in network penetration testing?

Cyphere helps organisations to improve their network security by providing detailed network penetration testing services designed to detect real-world risks across both internal and external environments. We offer network penetration testing services through a CREST-aligned methodology that includes reconnaissance, network mapping, vulnerability analysis, and safe exploit validation to identify weaknesses before malicious threat actors do. Customers benefit from clear insights into issues like misconfigurations, outdated systems, weak authentication, insecure network protocols, exposed services and paths that could allow attackers to gain higher access, which are problems our consultants regularly find.

Beyond detecting issues, Cyphere also ensures that its customers receive clear guidance, risk-based prioritisation, and remediation steps according to their infrastructure. What makes Cyphere different from others is the deep technical expertise, business-focused approach, and the commitment to deliver transparent and high-quality assessments that help organisations to reduce risk and improve their cybersecurity posture.

What are the benefits and dangers of network penetration testing

The top 5 benefits of network penetration testing are listed below.

1. Identifies vulnerabilities before hackers do: Network penetration testing provides organisations a clear view of weaknesses such as insecure services, exposed ports, weak firewall rules and configuration flaws before attackers can exploit them. This identification of vulnerabilities helps organisations fix issues early, reducing the risk of ransomware attacks, unauthorised access or service disruptions.
2. Strengthens network security controls: Network penetration testing evaluates whether firewalls, network segmentation, ACLs, IDS/IPS and other defensive controls are configured and functioning effectively or not. This helps organisations identify gaps that allow lateral movement, privilege escalation or data exposure.
3. Prevents costly data breaches: Network penetration testing helps organisations avoid the financial, operational and reputational impact of a breach by identifying attack paths and system weaknesses at an early stage.
4. Helps meet compliance requirements: Industries like finance, e-commerce and healthcare often require annual network pentesting for regulations such as ISO 27001, PCI DSS, GDPR and HIPAA. Network penetration testing helps organisations demonstrate compliance by validating that networks are secure and properly managed.
5. Improves incident response readiness: Network penetration testing simulates real-world attack scenarios, helping organisations understand how quickly and effectively their security teams can detect and respond to threats. This highlights gaps in monitoring, alerting and escalation processes.

Risks of network penetration testing are listed below.

1. Risk of system downtime or crashes: Aggressive scans or high-volume requests can overload servers or network devices, causing slowdowns or crashes. This disrupts business operations, impacts services and can lead to financial or reputational damage.
2. Possible data loss or corruption: Brute-force attempts, payload injections or misconfigured scripts may unintentionally modify or delete data. This leads to system instability, compliance issues and costly recovery efforts, especially where sensitive data is involved.
3. Potential network performance degradation: Intensive scanning and traffic generation can consume bandwidth and strain network equipment. This results in slow applications, employee disruption and false monitoring alerts that add operational noise.
4. Legal and compliance issues: Testing without proper written authorisation or stepping outside the scope can violate laws or contracts. This exposes organisations to fines, legal disputes, audit failures and reputational risks.
5. Inaccurate results if the scope is poorly defined: If key systems or IP ranges are incorrectly scoped, then vulnerabilities remain undiscovered, creating a false sense of security. Testing out-of-scope systems can also cause disruptions or compliance violations, reducing the value of the assessment.

How often is a network penetration test recommended?

Annual network penetration testing is the minimum recommended frequency for most organisations, with quarterly testing recommended for high-risk environments or those with frequent infrastructure changes.

The majority of cybersecurity experts recommend conducting network penetration tests at least annually, with more frequent testing for organisations with dynamic environments. According to Dr Kehinde Kenny Onayemi in his research Enhancing Academic Cybersecurity: Integrated Framework with Network Penetration Testing, published on October 3, 2023, 73.2% of respondents recommended quarterly technical assessments, including penetration testing, as the optimal frequency for effective risk management and compliance. However, many organisations conduct network pen tests annually, particularly when infrastructure changes are less frequent or budgets are constrained.

PCI Security Standards Council (PCI DSS), a widely accepted standard, requires external and internal penetration tests at least once every 12 months or immediately after any significant changes in the infrastructure or application.

What best practices should be followed while doing network penetration testing?

Best practices for network penetration testing are listed below.

1. Obtain legal permission & define scope: Always get written authorisation before testing and clearly define in-scope IP ranges, timelines, systems and testing limitations to avoid legal or operational issues.
2. Understand the network architecture: Understand network diagrams, VLANs, firewalls and asset inventories. This helps you plan effective attack paths and avoid testing irrelevant systems.
3. Use a methodical testing framework: Follow recognised methodologies like PTES (Penetration Testing Execution Standard), NIST SP 800-115, or OSSTMM to ensure consistent, repeatable and industry-standard testing quality. For web application components within the network, the OWASP Testing Guide provides additional guidance.
4. Maintain a secure testing environment: Use isolated machines, updated tools and encrypted storage to prevent accidental damage or malware infection during testing.
5. Perform comprehensive enumeration: Enumerate ports, shares, services and credentials thoroughly.
6. Validate findings through safe exploitation: Exploit vulnerabilities in a safe and controlled manner. Avoid actions that could crash systems unless the client approves stress testing.
7. Document every step and evidence: Keep logs of commands, outputs and screenshots. Proper documentation helps prove findings and support a strong remediation report.
8. Communicate regularly with stakeholders: Notify stakeholders of progress, disruptions or critical findings. Clear communication ensures quick risk mitigation and smoother assessment.
9. Prioritise risks based on impact: Rate vulnerabilities using organisational risk levels or CVSS. Focus on exploiting high-impact vulnerabilities first that threaten business operations.
10. Provide actionable remediation guidance: Every finding should include clear, practical steps to fix vulnerabilities to ensure the test leads to measurable security improvements.

What is the scope of network penetration testing?

The scope of network penetration testing defines which systems, IP ranges, network segments and infrastructure components are authorised for testing. A typical network penetration testing scope includes firewalls, routers, switches, servers, VPN gateways, wireless access points, network services (DNS, DHCP, SMTP), cloud network configurations and internal/external IP ranges. The scope document also specifies testing limitations, excluded systems, testing windows and rules of engagement.

What are the future trends of network penetration testing?

The future trends of network penetration testing are growing due to the strong market growth, high share for network penetration testing, increasing threat & compliance pressure, and challenges, but not retreat. The global penetration testing market is projected to grow at a very good compound annual growth rate (CAGR). For example, one forecast estimates a 14.4% CAGR between 2025 and 2035. A network-specific market report states that the network penetration testing services market is expected to grow at a 6.6% CAGR from 2025 to 2035.

Network pentesting specifically is expected to remain a major segment because infrastructure continues to expand (cloud, IoT). The demand for penetration testing is increasing as cyber threats are growing, putting companies under greater regulatory pressure to secure their network. The rise of remote working, cloud adoption and hybrid networks expands the attack surface, which pushes more organisations to invest in network pentesting.

According to the Penetration Testing Services Market Report 2025, the UK penetration testing services market was valued at USD 157.5 million in 2024 and forecasts a compound annual growth rate (CAGR) of about 17.5% over the next several years.

Should you learn network penetration testing in 2026?

Yes, you should learn network penetration testing in 2026. The demand for network security skills continues to grow as organisations expand their cloud networks, IoT ecosystems, remote infrastructure and hybrid environments. Network penetration testing is not declining; it is evolving with AI-driven threats, automated attack tools and more complex enterprise architectures, which makes this assessment even more valuable for the future.

Network penetration testing is moderately hard to learn due to its complexity and reliance on expert knowledge, but new AI-driven tools and educational platforms are making it more accessible.

You can start by building a foundation in networking (TCP/IP, DNS, subnets, VLANs, firewalls), then learn Linux commands and security concepts. Set up a home lab using VirtualBox, cloud labs or VMware from platforms like Hack The Box, TryHackMe and immersive labs. Use essential tools like Nmap, Metasploit, Wireshark, Burp Suite, Hydra and Nessus. Practice real-world scenarios like enumerating services, scanning local networks, exploiting vulnerabilities and documenting findings. Finally, pursue certifications like PNPT, CEH, eJPT, or OSCP to strengthen your professional credibility.