Network Security
Network security encompasses policies, practices, and technologies designed to protect network infrastructure, data in transit, and connected systems from unauthorized access, misuse, and attacks.
Overview
Security operates at every layer of the network stack — from physical security of cables to application-layer encryption. This section covers the critical protocols and technologies that protect network communications.
Security Layers
graph TD
A[Network Security] --> B[Perimeter Security]
A --> C[Transport Security]
A --> D[Access Control]
A --> E[VPN/Encryption]
B --> F[Firewalls]
B --> G[IDS/IPS]
C --> H[TLS/SSL]
C --> I[IPsec]
D --> J[802.1X]
D --> K[RADIUS/TACACS+]
E --> L[Site-to-Site VPN]
E --> M[Remote Access VPN]
Threat Categories
| Category | Examples | Mitigation |
|---|---|---|
| Eavesdropping | Packet sniffing, MITM | Encryption (TLS/IPsec) |
| Spoofing | IP/MAC spoofing | Authentication, ingress filtering |
| Denial of Service | SYN flood, DDoS | Rate limiting, firewalls, CDN |
| Man-in-the-Middle | ARP poisoning, DNS hijacking | TLS, certificate pinning |
| Unauthorized Access | Brute force, credential stuffing | Firewalls, MFA, VPN |
| Replay Attacks | Captured packets retransmitted | Nonces, timestamps, session tokens |
Key Concepts
- Confidentiality: Only authorized parties can read the data (encryption)
- Integrity: Data hasn’t been tampered with (hashing, MAC)
- Authentication: Verifying identity (certificates, passwords, tokens)
- Non-repudiation: Sender cannot deny sending (digital signatures)
Interview Questions
-
Q: What’s the difference between confidentiality and integrity? A: Confidentiality ensures data is secret (encrypted). Integrity ensures data hasn’t been modified (hashes/checksums). You can have integrity without confidentiality (checksum on plaintext) or confidentiality without integrity (encrypted but possibly tampered).
-
Q: What is defense in depth? A: Multiple layers of security controls. If one fails, others provide protection. Example: firewall + TLS + VPN + authentication + monitoring.
Summary
Network security is multi-layered. The pages in this section cover the specific protocols (TLS, SSL, IPsec) and technologies (firewalls, VPN) that implement security principles in practice.