A firewall monitors and controls incoming and outgoing network traffic based on predefined rules. It blocks unauthorised access while permitting legitimate communication. Can be hardware, software, or both.
Packet filtering: examines each packet's source/destination IP and port; blocks if it doesn't match rules
Stateful inspection: tracks the state of network connections; more sophisticated filtering
All organisations should have a firewall between their internal network and the internet
Wireless Security
Protecting Wi-Fi Networks
WPA2/WPA3 (Wi-Fi Protected Access): encrypts wireless traffic using AES. WPA3 is the current standard — stronger than WEP (outdated, easily cracked) and WPA.
MAC address filtering: only devices whose MAC (hardware) address is on an approved list can connect to the network. Can be bypassed by MAC spoofing but adds a layer of control.
SSID hiding: not broadcasting the Wi-Fi network name provides minimal security through obscurity
VPNs & Intrusion Detection
Advanced Network Protection
VPN (Virtual Private Network): creates an encrypted tunnel between your device and a VPN server. Hides your IP address and protects data on public Wi-Fi. Used by businesses for remote workers to securely access company networks.
IDS (Intrusion Detection System): monitors network traffic for suspicious patterns and alerts administrators to potential attacks.
Exam Practice
Have a go at this question
Edexcel-style question
Describe how a firewall protects a network and state one limitation.
3 marks
A firewall monitors network traffic and blocks packets that do not match its security rules [1], preventing unauthorised access to the network [1]. Limitation: it cannot protect against threats that originate from within the network, such as malware already installed by an insider [1].
Key Takeaways
What to Remember
Firewall: blocks unauthorised traffic based on rules; can be hardware or software
WPA3: current Wi-Fi encryption standard; MAC filtering: whitelist approved devices
VPN: encrypted tunnel; hides IP; secure for remote access and public Wi-Fi
Defence in depth: use multiple layers — firewall + encryption + authentication + IDS