Network Security Basics
Discover how networks are protected from unauthorized access, eavesdropping, and cyber attacks using firewalls, VPNs, and encryption.
Why Network Security?
Data flowing over networks is vulnerable to interception, manipulation, and unauthorized access. Network security involves the policies, processes, and technologies used to protect network infrastructure and data.
Core Pillars of Security (CIA Triad)
- Confidentiality — Ensuring only authorized users can read the data. Done via encryption.
- Integrity — Ensuring data is not altered or corrupted in transit. Done via hashing and digital signatures.
- Availability — Ensuring authorized users can access resources reliably. Guarded against DDoS attacks and hardware failures.
Firewalls
A firewall acts as a barrier between a trusted internal network and an untrusted external network (like the internet). It monitors and filters incoming and outgoing traffic based on security rules.
- Packet Filtering Firewall — Inspects individual packet headers (IP addresses, ports) and blocks them.
- Stateful Inspection Firewall — Keeps track of active connections. It only allows incoming traffic if it was requested by an internal device.
- Next-Generation Firewall (NGFW) — Performs deep packet inspection (DPI), checks content/payloads, and blocks malware or specific app features.
VPN (Virtual Private Network)
A VPN creates an encrypted tunnel across a public network (like the internet), allowing you to send and receive data securely as if your device was directly connected to the private network. It uses protocols like OpenVPN, IPsec, or WireGuard.
IDS & IPS (Intrusion Systems)
- IDS (Intrusion Detection System) — Monitors network traffic for suspicious activity and alerts administrators. (Passive)
- IPS (Intrusion Prevention System) — Monitors traffic AND actively blocks suspicious packets in real-time. (Active)
Wi-Fi Security Protocols
Wireless networks broadcast signals that anyone nearby can intercept. Wi-Fi security protocols encrypt this data:
- WEP (Wired Equivalent Privacy) — Legacy protocol. Extremely insecure and easily cracked in minutes. Do not use.
- WPA2 — The standard for many years. Uses AES encryption. Vulnerable to KRACK attacks but still widely used.
- WPA3 — The latest standard. Offers much stronger encryption and protections against offline password guessing.
Common Network Attacks
- Man-in-the-Middle (MitM) — An attacker intercepts communications between two devices (e.g., on a public Wi-Fi network).
- DDoS (Distributed Denial of Service) — Flooding a network or server with traffic from thousands of infected devices (botnets) to crash it.
- IP Spoofing — Sending packets with a forged source IP address to impersonate a trusted system.
What's Next?
Learn how secure web communication is achieved with HTTP & HTTPS, or explore how DNS is protected in DNS Explained.