# Computer Security - Grade 10 Notes

## Complete Chapter Notes with All Exercises - NEB Curriculum

## 🎯 Chapter Overview

In today's digital world, our computers store everything from personal photos and school projects to bank details and private messages. But just like we lock our homes to keep burglars out, we need to protect our computers from digital threats. Computer Security is like having a digital bodyguard for your computer and data.

This chapter will teach you about the various threats that can harm your computer and data, and more importantly, how to protect against them. From understanding viruses and malware to learning about firewalls and backup systems, you'll gain the knowledge to keep your digital life safe and secure.

**Weightage:** 6-8 marks in SEE examination  
**Time Required:** 10-12 periods

## 📚 Learning Objectives

After studying this chapter, you will be able to:

- Define computer security and understand its importance
- Identify different types of security threats (physical and non-physical)
- Explain malicious codes like viruses, worms, and trojans
- Understand information security measures
- Learn about hardware security and power protection
- Apply preventive measures to protect computer systems

## 🔒 1. Introduction to Computer Security

**Computer Security** is the protection of computer data, information, programs, and hardware from malicious attackers and accidental harm. It's like having multiple layers of protection around your digital assets.

### Why is Computer Security Important?

- **Data Protection**: Keeps your personal files, photos, and documents safe
- **Privacy**: Prevents unauthorized access to your private information
- **System Integrity**: Ensures your computer works properly without disruption
- **Financial Safety**: Protects against cyber theft and fraud

## ⚠️ 2. Computer Security Threats

A **Computer Security Threat** is anything that has the potential to cause harm to data, information, software, or hardware.

### Types of Security Threats

| Threat Type | Definition | Examples |
|-------------|------------|----------|
| **Physical Threats** | Threats that can physically damage computer hardware | Fire, theft, power failure, natural disasters, faulty wiring |
| **Non-Physical Threats** | Threats that attack through software or network | Viruses, malware, hacking, unauthorized access |

### Real-World Examples

- **Physical**: A power surge damaging your computer's motherboard
- **Non-Physical**: A virus deleting your important files

## 🦠 3. Malicious Code (Malware)

**Malicious Code** is harmful computer code designed to cause undesired effects, security breaches, or damage to a computer system.

### Types of Malicious Code

#### A. Computer Virus
- **Definition**: A destructive program that hides in host files and replicates itself
- **Characteristics**:
  - Hides inside other programs or files
  - Can replicate and spread to other files
  - Requires a host file to survive

**Destructive Tasks of Viruses:**
- Display unnecessary messages and images
- Run unwanted programs
- Delete or corrupt files
- Slow down computer performance

**Routes of Virus Transmission:**
- Using pirated software
- Sharing infected portable storage devices
- Downloading files from unreliable websites
- Exchanging data on networks
- Opening virus-infected emails

**Symptoms of Virus Infection:**
- Changes in file sizes
- Missing files or folders
- Unusual error messages
- Programs hang frequently
- Slow system performance

#### B. Computer Worms
- **Definition**: Malicious code that doesn't hide in files but spreads from computer to computer
- **Characteristics**:
  - Don't need host files
  - Can replicate themselves
  - Spread through networks, emails, and storage devices

#### C. Trojan Horse
- **Definition**: A destructive program that pretends to be useful but performs malicious actions
- **Characteristics**:
  - Appears as legitimate software
  - Doesn't replicate itself
  - Creates backdoors for attackers

### Other Types of Malware

| Malware Type | Description |
|--------------|-------------|
| **Spyware** | Monitors user activities and steals information |
| **Ransomware** | Locks files and demands payment for access |
| **Adware** | Shows unwanted advertisements |
| **Scareware** | Shows fake virus alerts to trick users |

## 🛡️ 4. Information Security Measures

**Information Security** is the protection of data, information, and software from being lost or damaged due to accidental or intentional harm.

### A. Authentication Systems

#### 1. Password Protection
- **Definition**: A secret word or sequence of characters that provides access
- **Why use passwords?**: To protect files from unauthorized users
- **Strong Password Guidelines**:
  - Use combination of letters, numbers, and symbols
  - Minimum 8 characters long
  - Avoid personal information
  - Use different passwords for different accounts

#### 2. Biometric Authentication
- **Definition**: Uses unique physical characteristics for identification
- **Examples**: Fingerprint, facial recognition, iris scan, voice recognition
- **Advantages**: Very difficult to fake or steal

### B. Cryptography
- **Definition**: The method of protecting data by converting it into unreadable format
- **Process**:
  1. **Encryption**: Converting readable text into unreadable format
  2. **Decryption**: Converting encrypted text back to readable format

```
Original Text → [Encryption] → Encrypted Text → [Decryption] → Original Text
"Hello"      →               → "Khoor"        →              → "Hello"
```

### C. Firewall
- **Definition**: A security barrier that protects computer systems from external threats
- **Types**:
  - **Software Firewall**: Installed on individual computers
  - **Hardware Firewall**: Physical device protecting entire networks

**Purposes of Firewall:**
- Block unwanted network traffic
- Protect private networks from unauthorized access
- Block unsuitable website content
- Prevent entry of viruses and worms

### D. Antivirus Software
- **Definition**: Programs that detect, prevent, and remove malicious software

**Popular Antivirus Software:**
- Kaspersky Antivirus
- Avira Antivirus
- Avast Antivirus
- AVG Antivirus
- Windows Defender

**Functions of Antivirus:**
- Real-time scanning
- Regular system scans
- Automatic updates
- Quarantine infected files

### E. Backup Systems
- **Definition**: Creating duplicate copies of data, information, and software

**Importance of Backup:**
- Protects against data loss
- Helps recover files if system crashes
- Protects against hardware failures
- Guards against accidental deletion

**Types of Backup:**
- **Full Backup**: Complete copy of all data
- **Incremental Backup**: Only changed files since last backup
- **Cloud Backup**: Data stored on remote servers

## 🔧 5. Hardware Security

**Hardware Security** refers to the protection of computer hardware from being damaged or lost.

### Hardware Security Measures

#### A. Regular Maintenance
- **Purpose**: Find problems before they cause major damage
- **Benefits**:
  - Keeps hardware in good working condition
  - Extends lifespan of components
  - Prevents unexpected failures

**Maintenance Activities:**
- Cleaning dust from components
- Checking cable connections
- Monitoring temperature
- Updating drivers

#### B. Environmental Protection
- **Air Conditioning**: Maintains optimal temperature
- **Dust Protection**: Prevents dust accumulation
- **Humidity Control**: Prevents moisture damage

#### C. Physical Security
- **Protection from theft**: Locks, security cameras (CCTV)
- **Fire protection**: Fire alarms, fire extinguishers
- **Insurance**: Financial protection against losses

### Power Protection Devices

**Power Protection Device** protects computer hardware from voltage fluctuations, power failures, and electrical surges.

| Device | Function |
|--------|----------|
| **UPS (Uninterruptible Power Supply)** | Provides backup power during outages |
| **Volt Guard** | Protects against voltage fluctuations |
| **Spike Guard** | Protects against power surges |
| **Stabilizer** | Maintains steady voltage output |
| **CVT (Constant Voltage Transformer)** | Regulates voltage automatically |

#### Role of UPS in Computer Security
- Provides backup power during outages
- Protects against voltage fluctuations
- Allows safe shutdown during power failures
- Protects files and operating system from corruption

## 📝 6. Preventive Measures

### Virus Prevention
- Stop using pirated software
- Install reliable antivirus software
- Scan computer regularly for viruses
- Install latest security patches
- Avoid suspicious email attachments
- Use trusted websites for downloads

### General Security Best Practices
- Keep software updated
- Use strong passwords
- Regular data backups
- Enable automatic updates
- Be cautious with email attachments
- Use secure networks

## 📋 7. Complete Exercise Solutions

### 1. Answer the following questions:

**a. What is meant by Computer Security?**

**Answer:** Computer Security is the protection of computer data, information, programs, and hardware from malicious attackers and accidental harm.

**b. What is computer Security threat? List its types.**

**Answer:** Computer Security threat is anything that causes loss or corruption of data, information, software, or physical damage to computer hardware. Its types are:
- Physical threats
- Non-physical threats

**c. What is malicious code? List any two examples.**

**Answer:** Malicious code is harmful computer code intended to cause undesired effects or damage to a computer system. Examples:
- Computer viruses
- Worms

**d. What is computer virus? List any two destruction tasks.**

**Answer:** Computer virus is a destructive program that disturbs normal functioning of a computer system. Destruction tasks:
- Display unnecessary messages and images
- Run unwanted programs

**e. What are the routes of computer virus transmission?**

**Answer:** Routes of virus transmission:
- Using pirated software
- Sharing infected portable storage devices
- Downloading files from unreliable websites
- Exchanging data on networks
- Opening virus-infected emails

**f. List any four symptoms of computer viruses.**

**Answer:** Symptoms of computer viruses:
- Changes in size of files
- Missing files or folders
- Unusual error messages appearing
- Programs hang frequently

**g. Write four preventive ways to protect computer system from viruses.**

**Answer:** Preventive measures:
- Stop using pirated software
- Install antivirus software
- Scan computer regularly for viruses
- Install latest security patch programs

**h. Define computer worm and trojan horse.**

**Answer:** 
- **Computer Worms:** Malicious code that doesn't hide in files and spreads from computer to computer through email, internet, and portable storage.
- **Trojan Horse:** Destructive program that pretends to be useful but performs malicious actions.

**i. What is information security? What does it do?**

**Answer:** Information Security is protection of data, information, and software from being lost or damaged due to accidental or intentional harm. It controls and prevents unauthorized access to data and information.

**j. List any four data and software security measures.**

**Answer:** Security measures:
- Firewall
- Antivirus software
- Authentication systems (Password and Biometric)
- Backing up data and software

### 2. Write appropriate technical terms:

| Description | Technical Term |
|-------------|----------------|
| Securing computer data from malicious attackers | Computer Security |
| Anything that can cause harm to data/software | Security Threat |
| Harmful computer code causing damage | Malicious Code |
| Destructive program that hides in host files | Computer Virus |
| Destructive program that doesn't hide but replicates | Computer Worms |
| Destructive program that doesn't replicate | Trojan Horse |
| Process of identifying authorized users | Authentication |
| Secret word providing system access | Password |
| Device reading biometric information | Biometric |
| Making data unreadable to unauthorized users | Cryptography |
| Converting encrypted text to original form | Decryption |
| Security barrier protecting from external threats | Firewall |
| Making extra copy of data | Backup |
| Device protecting from voltage fluctuations | Power Protection Device |
| Device providing backup electric power | UPS |

### 3. True/False Answers:

a. Data in disk cannot be damaged - **False**
b. Malicious code includes viruses, worms, trojans - **True**
c. Malicious website installs malware - **True**
d. Password prevents unauthorized access - **True**
e. Biometric locker prevents authorized person entry - **False**
f. Converting non-readable to readable is encryption - **False**
g. Hardware firewall blocks harmful internet data - **True**
h. Antiviruses are harmful programs - **False**
i. Regular maintenance detects hardware problems - **True**
j. Dust particles can damage hard disk - **True**
k. Volt guard supplies backup power during load shedding - **False** (UPS does this)

### 4. Full Forms:

- **FAT** = File Allocation Table
- **MALWARE** = Malicious Software
- **DDOS** = Distributed Denial of Service
- **SMPS** = Switched Mode Power Supply
- **CVT** = Constant Voltage Transformer
- **UPS** = Uninterruptible Power Supply
- **PSU** = Power Supply Unit
- **CCTV** = Closed Circuit Television

### 5. Multiple Choice Answers:

a. Data corruption causes: **iv. All of the above**
b. Physical threat includes: **iii. Stealing a computer**
c. Not malicious code: **iii. Kaspersky**
d. Computer virus is: **i. Malware**
e. Computer viruses can: **iv. All of the above**
f. Virus spread through: **iv. All of the above**
g. Information security measure: **i. Firewall**
h. Antivirus software: **iii. Kaspersky**
i. Backup power supplier: **iv. UPS**
j. Monitors online activities: **ii. Spyware**
k. Technique to steal credentials: **i. Phishing**

### 6. Matching:

- **Spam** → Unwanted advertisement messages
- **Browser Hijack** → Shows unwanted advertisements on browser
- **Scareware** → Shows fake virus alerts
- **Worm** → Makes network slow

## ✅ 8. Chapter Checklist & Exam Tips

**Exam Hotspots 🔥:**

- **Definitions**: Know exact definitions of computer security, malware types, and security measures
- **Security Threats**: Understand difference between physical and non-physical threats
- **Malware Types**: Be clear about viruses, worms, and trojans - their differences and characteristics
- **Prevention Methods**: Memorize virus prevention techniques and security measures

**Your Pre-Exam Checklist:**

- [ ] I can define computer security and its importance
- [ ] I can differentiate between physical and non-physical threats
- [ ] I understand all types of malicious code (viruses, worms, trojans)
- [ ] I know virus transmission routes and prevention methods
- [ ] I can explain information security measures (firewall, antivirus, etc.)
- [ ] I understand hardware security and power protection devices
- [ ] I can identify symptoms of virus infection

**Memory Tips:**
- **Virus vs Worm vs Trojan**: Virus hides, Worm spreads, Trojan tricks
- **Authentication methods**: Something you know (password), something you are (biometric)
- **Power devices**: UPS for backup power, Stabilizer for steady voltage

## 🎊 Conclusion

Computer Security is not just about installing antivirus software - it's about developing a security mindset. In our increasingly digital world, understanding these concepts will help you protect not just your school projects, but also your future digital assets and professional data.

Remember: A secure computer is like a well-protected house - it needs multiple layers of security, regular maintenance, and constant vigilance.

**Key to Success:** Understand Real-World Applications + Memorize Key Definitions + Practice Identifying Threats = Top Security Marks!