Computer Virus

Choose the correct option

Question 1

What does the letter V signify in the word VIRUS?

1. Vigilance
2. Vibrant
3. Vital
4. Variety

Answer

Vital

Reason — VIRUS stands for Vital Information Resources Under Siege.

Question 2

Which of the following can be infected by a computer virus?

1. Keyboard
2. CPU
3. Operating system
4. Printers

Answer

Operating system

Reason — A computer virus is a malicious program which primarily targets the Operating system software.

Question 3

Which of the following has the ability to replicate itself?

1. Worm
2. Trojan
3. Macro
4. Stealth

Answer

Trojan

Reason — Trojan doesn't replicate itself. They can spread only through user interactions.

Question 4

Through which of the following a computer can be infected with viruses?

1. Pen drive
2. E-mail
3. Accessing internet
4. All of the above

Answer

All of the above

Reason — All the three, Pen drive, E-mail and Accessing internet are sources of viruses.

Question 5

Which of the following is not an antivirus?

1. Norton
2. AVG
3. McAfee
4. Quick Heal

Answer

All the four options are Antivirus.

Reason — Norton is the antivirus product of the former Symantec Corporation.

State whether the following statements are True/False

Question 1

A computer shows unusual behaviour due to a virus attack.
True

Question 2

A computer virus is intentionally made to disturb the proper functioning of the computer system.
True

Question 3

A computer virus is destructive in nature.
True

Question 4

Unwanted mails in the spam folder can be a source of virus.
True

Question 5

A system restarting on its own is a symptom of a virus attack.
True

Question 6

A system gets affected by the virus automatically.
False

Question 7

A computer virus replicates itself within the amount of available memory.
True

Question 8

Antivirus software is specially designed to protect the entry of viruses into the system.
False

Question 9

The system gives an alarm, when a virus affected storage media is connected.
False

Question 10

Once an antivirus is loaded, your computer will never be affected by viruses.
False

Give two examples of each

Question 1

Boot Sector Virus

Answer

1. Danish boot
2. Quox

Question 2

Worm

Answer

1. Swen
2. Scalper

Question 3

Trojan

Answer

1. Backdoor
2. Nuker

Question 4

Macro

Answer

1. Bloodhound
2. Melissa

Question 5

Bomb

Answer

1. Saturday the 14^th
2. Happy Birthday 30

Question 6

Stealth

Answer

1. Frodo
2. Brain

Case-Study Based Questions

Question 1

Antivirus software are the utility programs that detect and prevent your computer system from attack of viruses. The main task of an antivirus software is to check all the programs/data files available in the computer. If a virus is detected, the antivirus clears it from the system. A pirated antivirus software should not be used because it will not be able to remove all the viruses, rather it may spread the virus itself. So, you are advised to install original antivirus software and keep it updating periodically. The updated antivirus software also takes care of newly created viruses.

With reference to the above case, answer the following questions:

(a) Which of the following statements is not true about antivirus software?

1. It locates infected files.
2. It searches for the viruses.
3. Once installed, it needs not be updated.
4. It removes viruses.

(b) Which of the following is not an antivirus software?

1. McAfee
2. AVG
3. GDATA
4. Google Chrome

(c) What is meant by pirated antivirus software?

1. Copied from original software
2. Reinstalled software
3. Loaded from original CD
4. None of the above

(d) What will happen if antivirus software is not updated periodically?

1. It will be erased after some time.
2. It will not be able to trace new viruses.
3. It will force operating system to stop functioning.

Answer

(a) Once installed, it needs not be updated.

(b) Google Chrome

(c) Copied from original software

(d) It will not be able to trace new viruses.

Define the following

Question 1

Define Worm

Answer

Worm — These viruses are programs which don't affect the functioning of a system. Once these viruses enter, they attack the security zone of a computer system. As a result, they just keep on replicating themselves in the disks.

They also spread through e-mail while using Internet. They use the address book of the system to send themselves through e-mails. These viruses drastically decrease the available memory of the system. For example- Swen, Scalper etc.

Question 2

Define Trojan

Answer

Trojan — These computer programs move around the valid programs and get executed with a flashy opening screen. They usually get into the system through e-mail attachments with fascinating names.

Once you open the e-mail, they become active in the background and slowly start deleting/corrupting the files inside the system. They can only spread through user interaction such as opening an e-mail attachment or downloading and running a file from the Internet. For example- Backdoor, Nuker ,etc.

Question 3

Define Bomb

Answer

Bomb — These viruses remain inactive for a long time and wait for a specific data or specific event for the disaster. The explosion takes place in the form of a sudden disaster inside the system.

For example, the virus 'Friday 13' waits for the day and date Friday the 13th to delete all the files of the system.

Question 4

Define Program Virus

Answer

Program Virus — These viruses directly attack the program files of the system with extensions like .EXE, .SYS, .COM, .DLL, etc. Once these programs files are infected with the virus, they start showing unusual behaviour. Since these viruses don't affect the boot sector, the system stays unaffected. When a relevant task related to a program file is performed, it becomes active and starts showing its destructive behaviour. For example, Sunday, Cascade, etc.

Short Answer Questions

Question 1

What is a computer virus?

Answer

Computer virus is a computer program which runs on any computer system without the user's knowledge. It is a malicious code that has the ability to duplicate and sends copies of itself to other computers through the Internet. Viruses can alter, corrupt and delete files, freeze your computer and interfere with the computer operation.

Question 2

Mention two ways of classifying a computer virus.

Answer

A computer virus can be classified into two categories based on their behaviour:

1. General infectors: These viruses infect the data files and application softwares of the computer system. They often make copies of themselves and try to reach other systems through e-mail. For example- worm, trojan and bomb.

2. System infectors: These viruses infect the files and system softwares of a computer system. As a result, the entire system crashes and the user is unable to work on the system. For example- boot sector virus, program virus, macro virus, stealth virus.

Question 3

Name the different sources of virus from which it may enter to a computer system.

Answer

The different sources of virus are:

1. A virus infected storage media viz. Compact Disc (CD), Digital Versatile Disc (DVD), pen drive, etc.
2. Pirated software (application/system)
3. Hired computer games or audio or video CD's.
4. Browsing or downloading unwanted sites through the internet.
5. Unwanted email attachments in the spam folder.

Question 4

Why is it necessary to update antivirus software installed in your computer system?

Answer

Everyday new types of viruses are being developed and an antivirus software might not be able to detect or eliminate them. So, it becomes necessary to keep the antivirus software updated against the new viruses.

Distinguish between the following

Question 1

Program Virus and Macro Virus

Answer

Question 2

Virus and Antivirus

Answer

Question 3

Worms and Viruses

Answer

Long Answer Questions

Question 1

What are the various ways to get virus attack to a computer system?

Answer

The various ways to get virus attack to a computer system are:

1. A virus infected floppy disk or other storage media like CD, DVD, pen drive can easily infect a system.
2. Pirated softwares
3. Hired computer games or audio or video CDs.
4. Browsing unwanted websites through Internet.
5. Unwanted mails in the spam folder.

Question 2

How will you detect that a computer system is infected by viruses?

Answer

We can detect that a computer system is infected by viruses if we notice one or more of these symptoms-

1. The speed of the processor becomes comparatively slow.
2. You may get unusual messages on the screen.
3. The disk drive light may constantly flash.
4. The opening or closing of programs/data files takes more time.
5. The programs may not run. Even if they run, they don't function properly.
6. The size of the infected file increases. Thus, the available memory decreases.
7. The system may frequently restart without the knowledge of the user.
8. The system may not be able to read the contents of CD/DVD/Pen drive.
9. The data files may corrupt or show unusual symbols/characters in place of the actual data.

Question 3

State the various ways to protect your system from viruses.

Answer

We can protect our system against viruses by following these measures:

1. Avoid using pirated CD/DVD to install any software in your system.
2. If you are using a Pen drive to transfer data to your system, make sure that the drive is free from virus.
3. If your system is connected to a LAN, keep a check on the users to avoid the misuse of the system.
4. Don't browse unwanted websites.
5. Install Antivirus software in your system.
6. Keep your antivirus software updated.
7. If you are using any external storage media to transfer data, scan the disc properly with Antivirus software.
8. Avoid reading unwanted e-mails while working with the e-mail account.
9. Always keep a backup copy of your program/data files.

Question 4

Why do people spread viruses? Explain.

Answer

One cannot understand the logic behind people's addiction to create and spread viruses. There are some reasons that might explain why people spread viruses:

1. They don't think about the consequences, others have to face.
2. They draw a false distinction between creating/publishing viruses and distributing them.
3. They consider it to be the responsibility of someone else to protect systems from their creations.
4. This is a way they fight with the authorities.
5. They think it is a way of getting attention/recognition from their peers.
6. They want to engage the antivirus vendors in a job.

Question 5

What is meant by an antivirus? Name different types of antivirus softwares.

Answer

An antivirus software is a computer program used to scan files. It detects, prevents, identifies and eliminates computer viruses and other malicious softwares. It also takes action to disarm or remove malicious software, such as viruses and worms, from a computer.

An antivirus software uses two different techniques to accomplish its job. They are:

1. Examining files to look for known viruses by means of a virus dictionary.
2. Identifying suspicious behaviour from any computer program which might indicate infection.

Examples of antivirus softwares are Kaspersky Antivirus, Quick Heal, Net Protector, AVG Antivirus, MCAfee etc.

Question 6

You have loaded 'Norton Antivirus' software in your computer system. Does it make your computer system free from virus attack for a lifetime? Justify.

Answer

No, loading of Norton antivirus software in your computer system doesn't make your computer system free from virus attack for a lifetime because everyday new types of viruses are being developed and an antivirus software might not be able to detect or eliminate them.

So, it is very important to keep your antivirus software updated against the new viruses. It can be done by using the Internet and checking for updates on a regular basis.

Question 7

What actions can an antivirus take, if a threat is detected in your computer system?

Answer

If a threat is detected in our computer system, our antivirus can take one or more of these actions in a specific order:

1. Repair — The antivirus tries to clean the infected file and remove the threat safely. This is important when it's our personal file and we would like to retain the data.

2. Quarantine — If repairing fails, the antivirus could choose to quarantine or isolate the infected file into a safe location. The quarantined file cannot be accessed but we will have a copy of the file. When a method of removing the threat is discovered, we can retrieve the data safely.

3. Delete — If the infected file can't be repaired and we do not want to retain the data, we can delete the files from our computer.