Introduction to Firewall

Introduction to Firewall

A firewall is a security device or software that monitors and controls network traffic based on predefined security rules.

It acts as a barrier between trusted internal networks and untrusted external networks (like the Internet).

🔹 Why Firewalls Are Important

• Prevent unauthorized access
• Protect systems from cyber attacks
• Control incoming and outgoing traffic
• Enforce security policies
• Monitor and log network activity

🔹 How a Firewall Works

A firewall inspects traffic and then:

• Allows traffic that matches security rules
• Blocks traffic that violates those rules

Rules are based on:

• Source & destination IP addresses
• Port numbers
• Protocols (TCP, UDP, ICMP)
• Application type

🔹 Types of Firewalls

1️⃣ Packet-Filtering Firewall

• Checks packet headers only
• Fast but limited security
• Works at Network layer (Layer 3)

2️⃣ Stateful Inspection Firewall

• Tracks active connections
• More secure than packet filtering
• Widely used in enterprise networks

3️⃣ Proxy Firewall (Application-Level)

• Acts as an intermediary
• Inspects application data
• Higher security, slower performance

4️⃣ Next-Generation Firewall (NGFW)

• Deep packet inspection
• Application awareness
• Intrusion prevention (IPS)
• Malware & URL filtering

🔹 Firewall Deployment Types

• Network Firewall – Protects entire networks
• Host-Based Firewall – Protects individual devices
• Cloud Firewall – Security for cloud workloads