Computer Virus
EXERCISES
Objective
I. Choose the correct option:
1. What does the letter V signify in the word VIRUS?
a) Vigilance. [ ]
b) Vibrant. [ ]
c) Vital. [✓]
d) Variety. [ ]
2. Which of the following can be infected by a computer virus?
a) Keyboard. [ ]
b) CPU. [ ]
c) Operating System. [✓]
d) Printers. [ ]
3. Which of the following has the ability to replicate itself?
a) Worm. [✓]
b) Trojan. [ ]
c) Macro. [ ]
d) Stealth. [ ]
4. Through which of the following a computer can be infected with viruses?
a) Pen drive. [ ]
b) E-mail. [ ]
c) Accessing internet. [ ]
d) All of the above. [✓]
5. Which of the following is not an antivirus?
a) Norton. [✓]
b) AVG. [ ]
c) McAfee. [ ]
d) Quick Heal. [ ]
II. State whether the following statements are True/False:
1. A computer shows unusual behaviour due to a virus attack. [T]
2. A computer virus is intentionally made to disturb the proper functioning of the computer system. [F]
3. A computer virus is destructive in nature. [T]
4. Unwanted mails in the spam folder can be a source of virus. [T]
5. A system restarting of its own is a symptom of a virus attack. [T]
6. A system gets affected by the virus automatically. [F]
7. A computer virus replicates itself within the amount of available memory. [T]
8. Antivirus software is specially designed to protect the entry of viruses into the system. [F]
9. The system gives an alarm, when a virus infected storage media is connected. [F]
10. Once an antivirus is loaded, your computer will never be affected by viruses. [F]
III. Give two examples of each:
1. Boot Sector Virus.
=
a) Danish boot.
b) Quox.
2. Worm.
=
a) Swen.
b) Scalper.
3. Trojan.
=
a) Backdoor.
b) Nuker.
4. Macro.
=
a) Bloodhound.
b) Melissa.
5. Bomb.
=
a) Jerusalem B.
b) Happy Birthday 30.
6. Stealth.
=
a) Frodo.
b) Brain.
IV. Case-Study Based Questions.
Unsolved
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 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?
i) It locates infected files. [ ]
ii) It searches for the viruses. [ ]
iii) Once installed, it needs not be updated. [✓]
iv) It removes viruses. [ ]
b) Which of the following is not an antivirus software?
i) McAfee. [ ]
ii) AVG. [ ]
iii) GDATA. [ ]
iv) Google Chrome. [✓]
c) What is meant by pirated antivirus software?
i) Copied from original software. [✓]
ii) Reinstalled software. [ ]
iii) Loaded from original CD. [ ]
iv) None of the above. [ ]
d) What will happen if antivirus software is not updated periodically?
i) It will be erased after some time. [ ]
ii) It will spread virus itself. [ ]
iii) It will not be able to trace new viruses. [✓]
iv) It will force operating system to stop functioning. [ ]
Subjective
I. Define the following:
1. Worm.
= A worm is a computer program that copies and multiples itself by using computer networks and security flaws.
2. Trojan.
= These are the programs that are destructive in nature and manipulates the user for its true intent.
3. Bomb.
= As the name suggests, the explosion of this virus takes place in the form of a sudden disaster inside the system. These viruses remains inactive for a long time and wait for a specific data or specific event for the disaster.
4. Program Virus.
= These viruses directly attack the program files of the system with extensions like .EXE, .SYS, .COM, .DLL, etc. One these program files are infected with the virus, they start showing unusual behaviour.
II. Short Answer Questions:
1. What is a computer virus?
= A computer virus is a malicious program which has the ability to execute and replicate itself. It is a human-made program, destructive in nature which usually attaches itself to other programs and spreads across the computer system.
2. Mention two ways of classifying a computer virus.
= Two ways of classifying a computer virus are -
i) General infectors;
ii) System infectors;
3. Name the different sources of virus from which it may enter to a computer system.
= The different sources of virus from which it may enter to a computer system are -
❐ A virus infected storage media viz. Compact Disc (CD), Digital Versatile Disc (DVD), pen drive, etc.
❐ Pirated software (application/system).
❐ Hired computer games or audio or video CDs.
❐ Browsing and downloading unwanted websites through the internet.
❐ Unwanted email attachments in the spam folder.
4. Why is it necessary to update antivirus software installed in your computer system?
= It is necessary to update antivirus software installed in your computer system 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 our antivirus software updated against the new viruses.
III. Distinguish between the following:
1. Program Virus and Macro Virus.
=
|
Program Virus |
Macro Virus |
|---|---|
|
1. These viruses directly attack the program files of the system with
extensions like .EXE, .SYS, .COM, .DLL, etc. |
2. These types of viruses attack the data files of the system. |
|
2. These viruses do not affect boot system. |
2. These viruses affect boot system. |
|
3. These viruses become active when relevant task related to a
program is performed. |
3. These viruses can easily spread from one computer to another
through the internet. |
2. Virus and Antivirus.
=
|
Virus |
Antivirus |
|---|---|
|
1. These are destructive malicious program which has the ability to
execute and replicate itself. |
2. These are the constructive programs to stop the virus attacks. |
|
2. These programs enter into computer system automatically. |
2. We have to install these programs into computer system of our own. |
|
3. These multiply themselves of themselves. |
3. We need to update these programs to detect new viruses. |
3. Worms and Viruses.
=
|
Worms |
Viruses |
|---|---|
|
1. Worms do not affect the functioning of a system. |
1. Viruses affect the functioning of a system. |
|
2. It drastically decreases the available memory of the system. |
2. It does not decrease the available memory of the system. |
|
3. These mainly spread through the computer networks and security
flaws. |
3. These spread through infected storage devices, pirated software,
hired softwares and so on. |
IV. Long Answer Questions:
1. What are the various ways to get virus attack to a computer system?
= The various ways to get virus attacks to a computer system are -
❐ A virus infected storage media viz. Compact Disc (CD), Digital Versatile Disc (DVD), pen drive, etc.
❐ Pirated software (application/system).
❐ Hired computer games or audio or video CDs.
❐ Browsing and downloading unwanted websites through the internet.
❐ Unwanted email attachments in the spam folder.
2. How will you detect that a computer system is infected by viruses?
= If our system is affected by a virus, we may notice one or more of the following symptoms -
❐ The speed of the processor becomes comparatively slow.
❐ You may get unusual messages on the screen.
❐ The disk drive light may constantly flash.
❐ The opening or closing of programs/data files takes more time.
❐ The programs may not run. Even if they run, they don't function properly.
❐ The size of the infected file increases. Thus, the available memory decreases.
❐ The system may frequently restart without the knowledge of the user.
❐ The system may not be able to read the contents of CD/DVD/pen drive.
❐ The data files may corrupt or show unusual symbols/characters in place of the actual data.
3. State the various ways to protect your system from viruses.
= It is always advised to take precautionary measures to protect our system from the virus attacks. We can protect our system against the viruses by following the these measures -
❐ Avoid using pirated CD/DVD to install any software in our system.
❐ If you are using a pen drive to transfer data to your system, make sure that the drive is free from virus.
❐ If our system is connected to a LAN (Local Area Network), keep a check on the users to avoid the misuse of the system.
❐ Don't browse unwanted websites.
❐ Install antivirus software in our system.
❐ Keep your antivirus software updated.
❐ If you are using any external storage media to transfer data, scan the disc properly with antivirus software.
❐ Avoid reading unwanted emails.
❐ Always keep a backup copy of your program/data files.
4. Why do people spread viruses? Explain.
= Viruses are the programs developed by humans. But, sometimes it becomes difficult to understand the reasons for why viruses are created. Some of the reasons for which a developer may create a virus program are -
❐ to test his programming skills.
❐ to merely carry out experiments.
❐ to take control of the computer and use it for malicious resolves.
❐ to make money.
❐ to steal sensitive information.
❐ to harm the other individual or an organisation.
5. What is meant by an antivirus? Name different types of antivirus software.
= Antivirus software are the utility programs (i.e., system software used to solve a particular computer problem) which detect and prevent viruses from attacking the system. The main task of an antivirus software is to check all the programs/data files available in the system. If virus is detected, the antivirus removes it and gets the system ready for the user.
Different types of antiviruses are -
❐ AVG Antivirus.
❐ Symantec Antivirus.
❐ McAfee.
❐ Quick Heal.
❐ Net Protector Antivirus.
❐ Kaspersky Antivirus.
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.
= If I have loaded Norton Antivirus software in my computer system. It does not make my computer system free from virus attack for life time 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 my Norton Antivirus updated against the new viruses.
7. What actions can an antivirus take, if a threat is detected in your computer system?
= If a threat is detected in our computer system, the following actions are taken by an antivirus -
❐ Repair : Usually, the first task of an antivirus is to clean the infected file and remove the threat safely. This is important when it's your personal file and you would like to retain the data.
❐ Quarantine : If repairing fails, the antivirus could choose to quarantine or isolate the infected file into a safe location. The file in quarantine cannot be accessed but we will have a copy of the file. When a method of removing the thread is discovered, we can retrieve our data safely.
❐ Delete : If the infected file can't be repaired and we don't want to retain the data, we have the choice to detect the antivirus program as well as the infected files from our computer.