Network Security
Network Security
1. Firewall
Firewall controls incoming and outgoing traffic.
Actions:
- Allow
- Block
- Filter
Types:
- Hardware firewall
- Software firewall
- Network firewall
- Application firewall (WAF)
2. VPN (Virtual Private Network)
VPN = Virtual Private Network
What it does:
- Encrypts internet traffic
- Hides IP
- Provides privacy
- Allows secure remote access
Useful for:
- Secure browsing on public WiFi
- Accessing blocked content
- Corporate secure connections
3. Proxy
A proxy acts as a middleman between user and internet.
Uses:
- Security
- Filtering
- Hiding identity
- Caching
4. Proxy vs VPN
| Feature | Proxy | VPN |
|---|---|---|
| Hides Identity | Yes | Yes |
| Encrypts Traffic | No | Yes |
| Security Level | Low | High |
| Speed | Faster | Slightly slower |
| Use Case | Basic anonymity | Full privacy & security |
5. SSL/TLS
SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) are the technology behind the Lock Icon in your browser.
How it works:
- Creates an encrypted tunnel between the client and server
- Handshake: Before sending data, the client and server agree on a secret code (keys) so that even if someone intercepts the data, it looks like gibberish
6. Public Key vs Private Key
| Feature | Public Key | Private Key |
|---|---|---|
| Who Owns It? | Shared with everyone | Kept secret by the owner |
| Security Level | Safe to share | Must never be shared |
| Used For | Encrypting data, verifying signatures | Decrypting data, creating signatures |
| Where It Lives | Servers, certificates, clients | Secure storage / device |
| Example Use | Website SSL certificates, sharing keys | Logging into SSH, signing JWT |
| Direction | Lock / Encrypt | Unlock / Decrypt |
| If Leaked? | Usually okay | Severe security risk |
Simple Understanding
- Public Key = Lock — Anyone can lock (encrypt) data for you
- Private Key = Key — Only you can unlock (decrypt) and access it
Encryption Flow
- Sender: Encrypts with Public Key
- Receiver: Decrypts with Private Key
Digital Signature Flow
- Sender: Signs with Private Key
- Receiver: Verifies with Public Key
7. SSH (Secure Shell)
SSH is a secure protocol used to remotely access and manage systems over a network.
- Default Port: 22
- Encrypted communication
- Key-based authentication supported
- Replaces insecure protocols like Telnet
For detailed SSH guide, see SSH
8. GATE Exam Important Points
- SSH provides encrypted remote login
- SSH port is 22
- VPN encrypts all traffic
- Proxy only hides identity
- SSL/TLS creates encrypted tunnel
Quick Reference
| Security Tool | Purpose | Port |
|---|---|---|
| Firewall | Traffic control | Various |
| VPN | Encrypted tunnel | Various |
| SSH | Secure remote access | 22 |
| SSL/TLS | Encrypted web traffic | 443 |