--- title: "Network security and firewalls" subject: "Computer Networks and Security" chapter: 8 key: "semester_7/computer_networks_and_security:network-security-firewall-protect" source: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/network-security-firewall-protect site: BCT Engineering --- # Network security and firewalls Computer Networks and Security · Chapter 8: Network Security - Asked in: 2069 Chaitra, 2+2+4 marks - Video: [What Is Firewall ? | Firewall Explained | Firewalls and Network Security | Simplilearn](https://www.youtube.com/watch?v=9GZlVOafYTg) — Simplilearn - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_7/computer_networks_and_security/network-security-firewall-protect - Whole chapter: https://www.bctengineer.com/md/semester_7/computer_networks_and_security/chapter-8 ## Question What is network security? How can firewalls enhance network security? Explain how firewalls can protect a system. ## Short answer Network security protects infrastructure and data, ensuring confidentiality, integrity, and availability. A firewall acts as a choke point filtering traffic, blocking unauthorized access, hiding addresses with NAT/DMZ, and using packet filtering, stateful inspection, proxies, logging, and default deny. It cannot stop insider attacks or traffic bypassing it. ## Answer #### Network security **Network security** is the protection of network infrastructure and the data carried on it from unauthorised access, misuse, modification or denial of service, so that the confidentiality, integrity and availability of information are kept. It uses tools such as encryption, authentication, firewalls, VPN and intrusion detection. #### How firewalls enhance network security A **firewall** is a hardware or software barrier between a trusted network and an untrusted network that filters traffic by a security policy. - It acts as a **single choke point** where all traffic is inspected and logged. - It blocks unauthorised inbound connections, port scans and known attack patterns. - It controls outbound traffic (stops malware calling out, restricts services). - It hides internal addresses using NAT / proxy. - It supports a **DMZ** for public servers and VPN termination. #### How a firewall protects a system 1. **Packet filtering:** checks IP addresses, ports and protocols against rules. 2. **Stateful inspection:** allows replies only to connections started inside. 3. **Proxy / application gateway:** inspects the application content (HTTP, FTP, SMTP) and hides the real server. 4. **Logging and alerts:** record suspicious events for the administrator. 5. **Default deny policy:** anything not explicitly allowed is blocked. ```text Internet --[ Firewall ]-- Internal LAN | DMZ (web, mail) ``` A firewall cannot stop attacks that bypass it (a modem, USB device), insider attacks, or viruses inside allowed traffic, so it is used with antivirus, IDS and encryption. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Why is a firewall a single choke point? A. It encrypts data B. All traffic passes through it for inspection and logging C. It blocks all traffic D. It routes packets Answer: B. Having one point makes policy enforcement possible. (Key point: Choke point) 2. What is a DMZ for? A. Keeping public servers apart from the internal LAN B. Encrypting email C. Routing D. Storing backups Answer: A. A DMZ hosts public web or mail servers. (Key point: DMZ) 3. How does stateful inspection protect? A. Inspects HTTP content B. Blocks everything C. Allows replies only to connections started inside D. Hides the server Answer: C. It tracks connections in a state table. (Key point: Stateful role) 4. What can a firewall not stop? A. Port scans B. Telnet C. Unauthorised inbound connections D. Attacks that bypass it, insider attacks, viruses in allowed traffic Answer: D. So it is used with antivirus, IDS and encryption. (Key point: Limitation) ## Related in Computer Networks and Security - [What is network security](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Anetwork-security-meaning) — Computer Networks and Security, chapter 8, asked 2× - [Firewall, its need and types](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Afirewall-types-working) — Computer Networks and Security, chapter 8, asked 7× - [What is a computer network](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Acomputer-network-definition) — Computer Networks and Security, chapter 1 - [Meaning of network architecture](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Anetwork-architecture-meaning) — Computer Networks and Security, chapter 1 - [Network design for 3-star hotel](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Ahotel-network-design) — Computer Networks and Security, chapter 1 - [X.25 network and features](https://www.bctengineer.com/question.md?key=semester_7%2Fcomputer_networks_and_security%3Ax25-network) — Computer Networks and Security, chapter 2 ## Related in other subjects - [Concept of power system security](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Apower-system-security-concept) — Power Plant Design, chapter 2, asked 3× - [Power system security and reserve requirement](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asecurity-reserve-requirement) — Power Plant Design, chapter 2 - [Power system security assessment](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Asecurity-assessment-components) — Power Plant Design, chapter 2 - [Accurate load forecasting and system security](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Aload-forecasting-benefits-security) — Power Plant Design, chapter 2