Network Security
Protecting the path
Network security is about controlling who and what can travel across a network.
Key devices and concepts
- Firewall: filters traffic by rules (address, port, protocol). It is the boundary control between networks.
- Router vs switch: a router moves traffic between networks; a switch connects devices within one network.
- VPN: creates an encrypted tunnel over an untrusted network such as the internet, protecting data in transit and masking the user's location.
- Encryption in transit: HTTPS (TLS) protects web traffic; unencrypted HTTP sends data in clear text.
- Wi-Fi security: WPA2 or WPA3 are current; WEP is obsolete and easily broken. Hiding the SSID or filtering MAC addresses is weak, not real security.
- Public vs private networks: a home LAN is private; the internet is public and untrusted.
Traps
- A firewall does not stop malware already inside the network, and it does not encrypt data.
- A VPN protects the connection, not the device - it will not stop a virus already on the laptop.
- "HTTPS means the site is trustworthy" is false; it only means the connection is encrypted. Phishing sites use HTTPS too.
- Open public Wi-Fi without a VPN exposes traffic to interception.
Rule of thumb: match the control to the layer - firewall for traffic, VPN for remote connections, WPA3 for wireless, HTTPS for web sessions.
Worked example: An employee works from a café on open Wi-Fi and must reach the company file server. The correct advice is to connect through the company VPN, because it encrypts the traffic end to end and prevents eavesdropping on the café network.