---
title: "Types of security attacks"
subject: "Operating System"
chapter: 8
key: "semester_6/operating_system:security-attacks-types"
source: https://www.bctengineer.com/q/semester_6/operating_system/security-attacks-types
site: BCT Engineering
---

# Types of security attacks

Operating System · Chapter 8: Security

- Asked in: 2071 Bhadra, 5 marks; 2073 Bhadra, 3.5 marks; 2070 Magh, 4 marks; year not given (asked 3 times)
- 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/security-attacks-types
- Whole chapter: https://www.bctengineer.com/md/semester_6/operating_system/chapter-8

## Question

Explain the different types of security attacks.

## Short answer

Security attacks are classified as passive (eavesdropping, traffic analysis) or active (masquerade, replay, modification, denial of service). Other common attacks include malware, trap doors, buffer overflows, phishing, and insider attacks. Attacks affect confidentiality, integrity, availability, or authenticity, countered by authentication, encryption, firewalls, and access control.

## Answer

A **security attack** is any attempt to break the confidentiality, integrity or availability of a system or its data. Attacks are classified as passive and active, and as coming from outside or inside.

#### 1. Passive attacks
The attacker only observes or copies data and does not change it, so they are hard to detect.
- **Release of message contents (snooping/eavesdropping):** reading private data, e.g. e-mail, passwords on the network.
- **Traffic analysis:** studying the pattern, size and frequency of messages even when they are encrypted.

#### 2. Active attacks
The attacker modifies data or disrupts service.
- **Masquerade (spoofing):** one entity pretends to be another, e.g. using a stolen password.
- **Replay:** a captured message is sent again to get an unauthorised effect.
- **Modification of messages:** altering part of a message.
- **Denial of service (DoS/DDoS):** flooding a server with requests so valid users cannot use it.

#### 3. Other common attacks (Tanenbaum)
- **Malware:** viruses, worms, Trojan horses, logic bombs, spyware.
- **Trap door (back door):** secret entry point left in a program.
- **Buffer overflow:** writing past the end of a buffer to overwrite the return address.
- **Login spoofing / phishing:** fake login screen collects passwords.
- **Insider attacks:** by users with legitimate access.

| Type | Effect on | Example |
|---|---|---|
| Interruption | Availability | DoS |
| Interception | Confidentiality | Sniffing |
| Modification | Integrity | Changing records |
| Fabrication | Authenticity | Fake messages |

Countermeasures: authentication, encryption, firewalls, antivirus, patches and access control.

## Check yourself

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

1. What separates passive from active attacks?
   A. Passive modify data; active only observe
   B. Passive come from inside; active from outside
   C. Passive only observe data; active modify data or disrupt service
   D. Passive use malware; active use eavesdropping
   Answer: C. Passive attacks such as snooping are hard to detect; active ones alter or disrupt. (Key point: Passive vs active)

2. What is traffic analysis?
   A. Flooding a server with requests
   B. Replaying a captured message
   C. Faking a login screen
   D. Studying the pattern, size and frequency of messages even if encrypted
   Answer: D. It is a passive attack that does not need to read content. (Key point: Traffic analysis)

3. Which is a denial-of-service attack and what does it affect?
   A. Flooding a server so valid users are refused; availability
   B. Reading mail in transit; confidentiality
   C. Changing records; integrity
   D. Inserting fake messages; authenticity
   Answer: A. DoS is an interruption attack on availability. (Key point: DoS)

4. What does a buffer overflow attack do?
   A. Copies passwords from the network
   B. Writes past the end of a buffer to overwrite the return address
   C. Pretends to be another user
   D. Leaves a secret entry in a program
   Answer: B. Overwriting the return address lets the attacker redirect execution. (Key point: Buffer overflow)

## 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