What is a Computer Virus?
Delhi Police Exam
This section covers essential cyber awareness concepts that frequently appear in Delhi Police Computer Awareness exams. Understanding computer viruses is crucial for both the exam and real-world digital safety.
1. What is a Computer Virus?
A computer virus is a malicious program that enters your system without permission and performs unwanted actions such as corrupting files, stealing data, or slowing performance.
It behaves just like a biological virus — it replicates itself and spreads from one computer to another.
Simple Definition:
A computer virus is a self-replicating harmful software that attaches itself to other programs or files and spreads when the infected program runs.
2. How Does a Virus Spread?
Through infected USB drives or external devices
By downloading unsafe files or attachments
From malicious websites or email links
Via pirated software or cracked versions
3. Major Types of Computer Viruses (For Exam)
Trojan Horse
Disguised as legitimate software but performs malicious activity in the background.
- Does not replicate itself
- Example: A fake game file that secretly steals passwords
💡 Trick to Remember: Trojan pretends to be a friend but attacks from inside.
Worm
A self-replicating program that spreads through networks without user action.
- Can cause network slowdown or crash
- Example: "ILOVEYOU" worm (famous global attack)
💡 Trick: Worm works alone and spreads fast.
Ransomware
Encrypts your files and demands money (ransom) to unlock them.
- Example: WannaCry ransomware (2017)
- Often spreads via email attachments
💡 Trick: Ransomware = Your files kidnapped for money.
Macro Virus
Infects software that uses macros like MS Word or Excel.
- Activated when you open an infected document
Boot Sector Virus
Attacks the boot area of storage devices (like hard drives).
- Activates when you start your system
4. Prevention Tips for Delhi Police Exam & Practice
Install and update antivirus software
Avoid clicking suspicious email links
Do not use unknown pen drives
Keep your Windows Firewall ON
Regularly backup important data
5. PYQ Style Questions
Which of the following is not a type of computer virus?
Options: (a) Trojan Horse (b) Worm (c) Ransomware (d) Bluetooth
Category: Virus Types
Show Answer
Bluetooth
A program that replicates itself and spreads without user's consent is called:
Options: (a) Trojan (b) Worm (c) Adware (d) Spyware
Category: Virus Behavior
Show Answer
Worm
Which of the following demands payment to decrypt files?
Options: (a) Spyware (b) Ransomware (c) Trojan (d) Adware
Category: Virus Function
Show Answer
Ransomware
A virus that attaches to Microsoft Word documents is called:
Options: (a) Boot Sector Virus (b) Macro Virus (c) Trojan (d) Worm
Category: Virus Types
Show Answer
Macro Virus
What is the full form of "WannaCry"?
Options: (a) A mobile OS (b) A ransomware virus (c) An antivirus (d) A search engine
Category: Famous Viruses
Show Answer
A ransomware virus
Short Task (Descriptive Practice)
Question:
Explain in 40–50 words how a computer virus spreads and how it can be prevented.
(Use real-life examples — e.g., email attachments or USB drives.)
Answer Guidelines:
Mention common spread methods like email attachments, USB drives, malicious websites
Include prevention methods like antivirus, avoiding suspicious links, regular updates
Sample Answer Structure:
Computer viruses spread through infected email attachments, USB drives, and malicious websites. They can be prevented by installing antivirus software, avoiding suspicious links, keeping systems updated, and not using unknown external devices. Regular backups also help recover data if infected.
Quick Recap (Memory Booster)
| Type | Main Feature | Trick to Remember |
|---|---|---|
| Trojan Horse | Looks useful but harmful | "Friend turns foe" |
| Worm | Self-replicating | "Worm works alone" |
| Ransomware | Locks data for money | "Files kidnapped" |
| Macro Virus | Infects Word/Excel | "Document danger" |
| Boot Sector Virus | Damages startup area | "Boot = Start" |
Exam Strategy Tip: In Delhi Police papers, virus-related MCQs usually test definition, type recognition, and prevention steps — 1 to 2 marks sure-shot area.
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