---
title: "Internet-connected system threats"
subject: "Operating System"
chapter: 8
key: "semester_6/operating_system:internet-security-threats"
source: https://www.bctengineer.com/q/semester_6/operating_system/internet-security-threats
site: BCT Engineering
---

# Internet-connected system threats

Operating System · Chapter 8: Security

- Asked in: 2072 Magh, 6 marks
- Video: [Operating System Security: Threats, Attacks & Defense (Beginner's Guide)](https://www.youtube.com/watch?v=RVyvehsp0Fk) — CodeLucky
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/operating_system/internet-security-threats
- Whole chapter: https://www.bctengineer.com/md/semester_6/operating_system/chapter-8

## Question

The use of internet is a possible cause of a security breach. Describe the major threats by which a system connected to the internet is always prone to attack. Explain.

## Short answer

Internet-connected systems face viruses/worms, Trojans/spyware, DoS/DDoS, eavesdropping, spoofing/phishing, buffer overflows, man-in-the-middle attacks, password attacks, malicious mobile code, and social engineering. Countermeasures include firewalls, antivirus, patching, encryption (SSL/TLS, VPN), strong authentication, intrusion detection, regular backups, and user awareness training.

## Answer

A system connected to the Internet can be reached by anyone in the world, so it faces the following major threats.

1. **Viruses and worms:** malicious code spreading through e-mail attachments, downloads and network services. The Morris worm and later Internet worms spread through vulnerable services without user action.
2. **Trojan horses and spyware:** programs that look useful but steal data or open the system to attackers.
3. **Denial of Service (DoS/DDoS):** flooding a server with many requests (often from a botnet) so legitimate users cannot be served.
4. **Eavesdropping/sniffing:** capturing passwords and data travelling in plain text across the network.
5. **Spoofing and masquerading:** forging IP addresses, e-mail senders or web sites (phishing) to trick users.
6. **Buffer overflow and exploiting software bugs:** attackers send specially crafted input to run their own code.
7. **Man-in-the-middle and replay attacks:** the attacker intercepts and alters or resends messages.
8. **Password attacks:** guessing, dictionary attacks and brute force.
9. **Malicious mobile code:** harmful ActiveX controls, Java applets or JavaScript downloaded from web pages.
10. **Social engineering:** deceiving users into disclosing information.

#### Countermeasures
Firewalls, antivirus, patching, encryption (SSL/TLS, IPsec, VPN), strong authentication, intrusion detection systems, regular backups and user awareness.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. How does a DDoS attack work?
   A. Many requests, often from a botnet, flood a server so legitimate users cannot be served
   B. It reads passwords in plain text
   C. It forges the sender address
   D. It hides in an attachment
   Answer: A. It targets availability. (Key point: DoS)

2. What is eavesdropping/sniffing?
   A. Guessing passwords
   B. Capturing passwords and data sent in plain text over the network
   C. Fake web sites
   D. Sending crafted input to run code
   Answer: B. Encryption (SSL/TLS, VPN) is the defence. (Key point: Sniffing)

3. What does man-in-the-middle do?
   A. Floods the server
   B. Sneaks in a back door
   C. Intercepts and alters or resends messages
   D. Guesses passwords
   Answer: C. It combines interception with modification or replay. (Key point: Man in the middle)

4. What is spoofing?
   A. Capturing network traffic
   B. Encrypting files
   C. Overflowing a buffer
   D. Forging IP addresses, e-mail senders or sites to trick users
   Answer: D. Phishing is a spoofing example. (Key point: Spoofing)

## Related in Operating System

- [Attack types; security of all components](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Aattack-types-security-protection-components) — Operating System, chapter 8
- [Types of security attacks](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Asecurity-attacks-types) — Operating System, chapter 8, asked 3×
- [Short note: information security model](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Ainfo-security-model-note) — Operating System, chapter 8
- [Short note: security policy](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Asecurity-policy-note) — Operating System, chapter 8
- [Authentication as security mechanism](https://www.bctengineer.com/question.md?key=semester_6%2Foperating_system%3Aauthentication-security) — Operating System, chapter 8

## Related in other subjects

- [Threats, controls and security measures](https://www.bctengineer.com/question.md?key=semester_8%2Finformation_system%3Asecurity-threats-controls-measures) — Information System, chapter 2, asked 3×
- [IS security threats and safeguards](https://www.bctengineer.com/question.md?key=semester_8%2Finformation_system%3Ais-security-threats-controls) — Information System, chapter 2
- [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