Concept of Computer Virus
A computer virus is a type of malicious software (malware) that is designed to replicate itself and spread from one system to another, often damaging data, corrupting files, or slowing down performance.
Analogy: Just like a biological virus infects humans, a computer virus infects computers.
🕰️ History of Computer Viruses
| Year | Event |
|---|---|
| 1971 | Creeper virus – First known experimental self-replicating program. Displayed: “I’m the creeper, catch me if you can.” |
| 1986 | Brain virus – First PC virus created by two Pakistani brothers. Spread via floppy disks. |
| 1987 | Vienna virus – One of the first viruses to be detected by an antivirus. |
| 1988 | First antivirus software – Developed to combat Vienna and other viruses. |
| 2000s | Rise of email viruses like "ILOVEYOU" and worms like "Blaster." |
| 2010s | Advanced malware like Stuxnet, Ransomware (WannaCry). |
| 2020s | Viruses target cloud, IoT, and mobile platforms. |
🧬 Types of Computer Viruses
| Type | Description |
|---|---|
| File Infector | Attaches to program files like .exe. |
| Boot Sector Virus | Infects master boot record (MBR) of hard drive. |
| Macro Virus | Targets documents like Word/Excel using macros. |
| Polymorphic Virus | Changes code to avoid detection. |
| Worms | Self-replicating malware that spreads through networks. |
| Trojan Horse | Pretends to be useful software but contains malware. |
| Ransomware | Locks or encrypts files and demands ransom. |
| Spyware | Secretly collects user data. |
| Adware | Automatically displays unwanted ads. |
🛡️ What is Antivirus?
An antivirus is a software designed to detect, prevent, and remove viruses and malware from your computer.
Functions:
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Scanning files and programs
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Quarantining or deleting infected files
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Real-time protection
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Updating virus definitions
Examples:
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Quick Heal
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Norton
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McAfee
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Avast
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Kaspersky
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Windows Defender
⭐ Important Points
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"Creeper" was the first experimental virus.
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"Brain" was the first virus for MS-DOS.
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Viruses spread via email, USB, websites, networks.
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Antivirus software must be updated regularly.
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Use firewalls, secure browsing, and backups to stay safe.
✅ MCQ Questions
Q1. What was the first computer virus in the world?
A) Brain
B) Creeper
C) ILOVEYOU
D) Melissa
✔️Answer: B) Creeper
Q2. Which type of virus attaches itself to executable programs?
A) Macro virus
B) Boot sector virus
C) File infector
D) Trojan
✔️Answer: C) File infector
Q3. Which of the following is not a feature of antivirus software?
A) Removing malware
B) Creating malware
C) Quarantining infected files
D) Real-time scanning
✔️Answer: B) Creating malware
Q4. What does a Trojan horse do?
A) Replicates itself
B) Pretends to be useful but is harmful
C) Infects boot sector
D) Encrypts data and demands ransom
✔️Answer: B) Pretends to be useful but is harmful
Q5. Which virus encrypts your files and demands payment?
A) Worm
B) Macro
C) Ransomware
D) Spyware
✔️Answer: C) Ransomware
Q6. The "Brain" virus was created in which country?
A) India
B) USA
C) Pakistan
D) China
✔️Answer: C) Pakistan
Q7. A self-replicating malware that spreads without human action is called:
A) Trojan
B) Virus
C) Worm
D) Macro
✔️Answer: C) Worm