## What is a Firewall? - A firewall acts as a security barrier between trusted internal networks and untrusted external ones. - It monitors and controls incoming and outgoing network traffic based on security rules. --- ## How Firewalls Work - Examine data packets to decide whether to **allow** or **deny** them. - Implement rules based on the 5 tuples: - **Source/Destination IP** - **Source/Destination Port** - **Protocol** --- ## Firewall Techniques 1. **Packet Filtering**: - Inspects packets individually based on predefined rules. 2. **Stateful Inspection**: - Tracks the state of active connections to make more informed decisions. 3. **Next-Generation Firewalls (NGFW)**: - Incorporate advanced features like deep packet inspection and intrusion prevention. --- ## Best Practices - Follow the Principle of Least Privilege: Only permit necessary traffic and block all else - Use Specific Rules: Specify exact IP ranges, ports, and protocols to control traffic - Enable Logging and Monitoring: Track which rules are being triggered to identify unusual traffic patterns and potential security incidents.