4.2.1 Network security
Why Network Security Matters
A network that is accessible to attackers puts data, systems and users at risk. Without adequate security, networks are vulnerable to unauthorised access, data theft, service disruption, malware spread and financial fraud. Network security involves both identifying vulnerabilities before they are exploited and implementing measures to prevent exploitation.
Identifying Network Vulnerabilities
Penetration Testing
Penetration testing (pen testing) is an authorised, simulated cyberattack carried out by security professionals to identify weaknesses in a network or system. A penetration tester attempts to break into the network using the same techniques a real attacker would use — attempting to bypass firewalls, exploit software vulnerabilities, crack passwords or intercept traffic.
- Always carried out with explicit permission from the organisation
- Results in a report identifying found vulnerabilities and recommended fixes
- Performed periodically (e.g. annually) or after major changes to the system
Ethical Hacking
Ethical hacking is a broader term for any authorised security testing using hacking techniques. Penetration testing is one type of ethical hacking. Ethical hackers may also conduct:
- Vulnerability scanning: automated tools scan the network for known weaknesses
- Social engineering tests: testing whether employees can be tricked into revealing credentials (e.g. phishing simulations)
- Physical security tests: attempting to gain physical access to server rooms
The key distinction between ethical and malicious hacking is authorisation — ethical hackers have written permission and report findings to improve security.
Protecting Networks
| Method | How it works |
|---|---|
| Access control | Restricts who can access the network and what they can do. Includes strong authentication (passwords, multi-factor authentication), user accounts with appropriate permissions, and network access control lists (ACLs) that determine which devices and users are allowed to connect. Principle: users have access only to the resources they need. |
| Physical security | Protects the physical hardware from unauthorised physical access. Includes locked server rooms with keycard access, CCTV surveillance, securing network ports (disabling unused ports), cable locks on hardware and environmental controls (fire suppression, cooling). An attacker with physical access to a server can bypass many software security measures. |
| Firewalls | A firewall monitors and controls incoming and outgoing network traffic based on predefined security rules. It acts as a barrier between a trusted internal network and untrusted external networks (e.g. the internet). Firewalls can block traffic on specific ports, filter packets by IP address, and detect suspicious patterns. Software firewalls run on individual devices; hardware firewalls protect entire networks. |
Key Takeaways
- Penetration testing and ethical hacking are authorised methods of identifying vulnerabilities before attackers do.
- Access control limits who can access the network and its resources.
- Physical security prevents unauthorised physical access to hardware.
- Firewalls filter traffic between trusted and untrusted networks based on rules.
- Effective network security uses multiple layers — no single method is sufficient alone.