Skip to main content

Network security and firewalls

Short answer

Network security protects infrastructure and data, ensuring confidentiality, integrity, and availability. A firewall acts as a choke point filtering traffic, blocking unauthorized access, hiding addresses with NAT/DMZ, and using packet filtering, stateful inspection, proxies, logging, and default deny. It cannot stop insider attacks or traffic bypassing it.

What is network security? How can firewalls enhance network security? Explain how firewalls can protect a system.

Network security

Network security is the protection of network infrastructure and the data carried on it from unauthorised access, misuse, modification or denial of service, so that the confidentiality, integrity and availability of information are kept. It uses tools such as encryption, authentication, firewalls, VPN and intrusion detection.

How firewalls enhance network security

A firewall is a hardware or software barrier between a trusted network and an untrusted network that filters traffic by a security policy.

  • It acts as a single choke point where all traffic is inspected and logged.
  • It blocks unauthorised inbound connections, port scans and known attack patterns.
  • It controls outbound traffic (stops malware calling out, restricts services).
  • It hides internal addresses using NAT / proxy.
  • It supports a DMZ for public servers and VPN termination.

How a firewall protects a system

  1. Packet filtering: checks IP addresses, ports and protocols against rules.
  2. Stateful inspection: allows replies only to connections started inside.
  3. Proxy / application gateway: inspects the application content (HTTP, FTP, SMTP) and hides the real server.
  4. Logging and alerts: record suspicious events for the administrator.
  5. Default deny policy: anything not explicitly allowed is blocked.
Internet --[ Firewall ]-- Internal LAN
               |
              DMZ (web, mail)

A firewall cannot stop attacks that bypass it (a modem, USB device), insider attacks, or viruses inside allowed traffic, so it is used with antivirus, IDS and encryption.

✓ Answer checked by Claude Opus 5.5 (high effort)

Related questions

All Computer Networks and Security chapter 8 questions →