Malware (CBSE Class 11 Computer Science)

Computers, smartphones, and digital devices are essential for education, business, banking, communication, and entertainment. However, they are also vulnerable to malicious software that can damage systems, steal information, display unwanted advertisements, or disrupt normal operations. Such harmful software is collectively known as Malware.

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Learning Objectives

• Understand Malware.
• Learn different types of malware.
• Understand Viruses, Trojans, and Adware.
• Identify symptoms of malware infection.
• Learn methods of malware prevention.
• Develop safe computing habits.

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What is Malware?

The word Malware is formed by combining the words Malicious and Software.

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Objectives of Malware

• Steal confidential information.
• Damage files.
• Slow down computer performance.
• Display unwanted advertisements.
• Gain unauthorized access.
• Monitor user activities.

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Types of Malware (CBSE Syllabus)

          Malware

             │

     ┌───────┼────────┐

     │       │        │

   Virus   Trojan   Adware

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How Malware Enters a Computer

Unknown Email

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Downloaded File

       │

Infected USB

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Unsafe Website

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Pirated Software

       │

Malware Infection

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1. Virus

A computer virus usually requires user action, such as opening an infected file or running an infected program, to spread.

Characteristics of a Virus

• Attaches to other files or programs.
• Replicates itself.
• Requires user action to spread.
• May corrupt or delete files.
• Can slow down the computer.

Examples of Damage

• Deleting important files.
• Corrupting documents.
• Slowing system performance.
• Causing frequent crashes.

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2. Trojan (Trojan Horse)

Unlike a virus, a Trojan does not usually replicate itself. Instead, it may create a backdoor, steal information, or provide unauthorized access to attackers.

Characteristics of a Trojan

• Appears to be genuine software.
• Tricks users into installation.
• May steal passwords.
• May allow remote access to attackers.
• Does not normally self-replicate.

Examples

• Fake antivirus software.
• Cracked games containing hidden malware.
• Fake software updates.

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3. Adware

Some adware is legitimate and supported by advertising, while malicious adware may collect browsing information or redirect users to unsafe websites without consent.

Characteristics of Adware

• Displays frequent advertisements.
• May redirect web browsers.
• Can slow browsing speed.
• May collect browsing information.

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Comparison of Malware

Type	Main Purpose	How it Works
Virus	Damage files	Attaches to files and spreads when executed
Trojan	Steal information	Disguises itself as genuine software
Adware	Display advertisements	Shows unwanted advertisements

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Symptoms of Malware Infection

• Computer becomes unusually slow.
• Frequent system crashes.
• Unexpected pop-up advertisements.
• Programs open automatically.
• Unknown software appears.
• Files become corrupted or inaccessible.
• Browser homepage changes without permission.
• Unusual network activity.

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How Malware Spreads

• Email attachments.
• Unsafe websites.
• Pirated software.
• Cracked games.
• USB drives.
• Fake software updates.
• Untrusted mobile applications.

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Current Affairs & CBSE Connect

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Did You Know?

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Cyber Alert

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How to Prevent Malware Infection

Following good cyber safety practices can greatly reduce the risk of malware infections.

Preventive Measures

• Install software only from trusted and official websites.
• Keep the operating system updated.
• Use a reliable antivirus or anti-malware program.
• Avoid opening suspicious email attachments.
• Do not click unknown links.
• Scan USB drives before opening files.
• Avoid downloading pirated software or games.
• Regularly back up important files.
• Enable automatic security updates.
• Remove unused software and browser extensions.

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Antivirus Software

Functions of Antivirus Software

• Detect malware.
• Scan files and folders.
• Remove infected files where possible.
• Quarantine suspicious files.
• Provide real-time protection.
• Protect against newly discovered threats through regular updates.

Examples

• Microsoft Defender
• Quick Heal
• Norton
• Kaspersky
• Bitdefender

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What is Quarantine?

Quarantine is a security feature in antivirus software that isolates suspicious or infected files so they cannot run or spread while allowing the user or antivirus software to decide whether to delete or restore them.

Detected Malware

        │

        ▼

   Quarantine

        │

 ┌──────┴──────┐

 │             │

Delete      Restore (Only if Safe)

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Safe USB Usage

• Scan every USB drive before opening files.
• Do not use unknown USB devices.
• Avoid running unknown executable files.
• Safely eject USB devices after use.
• Keep important files backed up.

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Safe Download Checklist

Practice	Safe?
Download from official website	✔ Yes
Read software reviews	✔ Yes
Install cracked software	✘ No
Ignore browser security warnings	✘ No
Scan downloaded files	✔ Yes

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Browser Extension Safety

Browser extensions can improve productivity, but untrusted extensions may collect personal information or inject advertisements.

Guidelines

• Install extensions only from official browser stores.
• Read reviews and ratings.
• Check requested permissions.
• Remove unused extensions.
• Keep extensions updated.

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Mobile Malware Awareness

Smartphones can also be affected by malware through unsafe apps, fake updates, or malicious links.

Safety Tips

• Install apps only from trusted app stores.
• Review app permissions carefully.
• Keep the operating system updated.
• Avoid rooting or jailbreaking devices unless you understand the security implications.
• Do not install unknown APK files.

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AI-generated Malware Awareness

Note: This topic is included only for awareness and is beyond the CBSE syllabus.

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Real-Life Example

A student downloads a free game from an unofficial website. After installation, numerous advertisements begin appearing, the browser homepage changes automatically, and the computer becomes slow.

This is an example of an Adware infection.

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Case Study

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Digital Hygiene Activity

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Teacher Activity

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Do's and Don'ts

Do's	Don'ts
Install antivirus software.	Install cracked software.
Download from official websites.	Open unknown email attachments.
Keep software updated.	Ignore security updates.
Scan USB drives.	Use unknown USB devices without scanning.
Backup important files.	Disable antivirus protection.

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Common Myths vs Facts

Myth	Fact
Only computers can get malware.	Smartphones and tablets can also be infected.
Free software is always safe.	Software should be downloaded only from trusted sources.
Antivirus removes every threat instantly.	Regular updates and safe user behaviour are equally important.
Mac and Linux systems can never get malware.	All operating systems can be targeted, although threats may differ.
If my computer is working, it cannot be infected.	Some malware operates silently without obvious symptoms.

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Quick Revision Box

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Memory Trick

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Exam Tips

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CBSE Competency-Based Questions

Question 1

A student installs a free video editing application from an unofficial website. Soon after installation, unwanted advertisements begin appearing and the browser homepage changes automatically.

1. Identify the malware.
2. Suggest three preventive measures.

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Question 2

A computer becomes unusually slow after opening an email attachment from an unknown sender.

1. What could be the possible reason?
2. What immediate steps should the user take?

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Assertion–Reason Questions

1.

Assertion (A): A Trojan normally disguises itself as legitimate software.

Reason (R): It attempts to trick users into installing it.

Answer: Both A and R are true, and R is the correct explanation of A.

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2.

Assertion (A): Antivirus software helps detect malware.

Reason (R): Antivirus software scans files and monitors suspicious activities.

Answer: Both A and R are true, and R is the correct explanation of A.

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Case-Based Question

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Multiple Choice Questions (MCQs)

1. Malware stands for:

1. Managed Software
2. Malicious Software
3. Modern Software
4. Manual Software

Answer: B

Explanation: Malware is short for malicious software designed to harm computers or users.

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2. Which malware attaches itself to files and spreads when they are executed?

1. Adware
2. Trojan
3. Virus
4. Firewall

Answer: C

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3. Which malware disguises itself as genuine software?

1. Virus
2. Trojan
3. Adware
4. Spyware

Answer: B

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4. Which malware mainly displays unwanted advertisements?

1. Virus
2. Trojan
3. Adware
4. Worm

Answer: C

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5. Which feature of antivirus software isolates suspicious files?

1. Firewall
2. Backup
3. Quarantine
4. Compression

Answer: C

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Short Answer Questions

1. Define Malware.
2. What is a Virus?
3. What is a Trojan?
4. Define Adware.
5. List any four symptoms of malware infection.
6. How does antivirus software help?
7. What is Quarantine?
8. State four methods of preventing malware infections.

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Long Answer Questions

1. Explain Malware and its different types with suitable examples.
2. Differentiate between Virus, Trojan, and Adware.
3. Discuss the symptoms of malware infection and preventive measures.
4. Explain the role of antivirus software in protecting computers.

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Frequently Asked Questions (FAQs)

1. What is Malware?

Malware is malicious software designed to damage, disrupt, or gain unauthorized access to computer systems or data.

2. What is the difference between a Virus and a Trojan?

A Virus attaches to files and spreads when executed, whereas a Trojan disguises itself as legitimate software to deceive users.

3. What does Adware do?

Adware displays unwanted advertisements and may collect browsing information.

4. Why should antivirus software be updated regularly?

Regular updates help the antivirus detect newly discovered malware threats.

5. Is downloading software from unofficial websites safe?

No. Software should always be downloaded from trusted and official sources.

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Summary

• Malware is malicious software designed to harm or misuse computer systems.
• The CBSE syllabus covers three common types of malware: Virus, Trojan, and Adware.
• Malware often spreads through unsafe downloads, infected USB drives, malicious email attachments, and suspicious websites.
• Antivirus software, regular updates, safe browsing, and responsible downloading practices help protect devices.
• Awareness and good digital hygiene are the best defenses against malware.

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