Choose the correct option
What does the letter V signify in the word VIRUS?
Reason — VIRUS stands for Vital Information Resources Under Siege.
Which of the following can be infected by a computer virus?
- Operating system
Reason — A computer virus is a malicious program which primarily targets the Operating system software.
Which of the following has the ability to replicate itself?
Reason — Trojan doesn't replicate itself. They can spread only through user interactions.
Through which of the following a computer can be infected with viruses?
- Pen drive
- Accessing internet
- All of the above
All of the above
Reason — All the three, Pen drive, E-mail and Accessing internet are sources of viruses.
Which of the following is not an antivirus?
- Quick Heal
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
A computer shows unusual behaviour due to a virus attack.
A computer virus is intentionally made to disturb the proper functioning of the computer system.
A computer virus is destructive in nature.
Unwanted mails in the spam folder can be a source of virus.
A system restarting on its own is a symptom of a virus attack.
A system gets affected by the virus automatically.
A computer virus replicates itself within the amount of available memory.
Antivirus software is specially designed to protect the entry of viruses into the system.
The system gives an alarm, when a virus affected storage media is connected.
Once an antivirus is loaded, your computer will never be affected by viruses.
Give two examples of each
Boot Sector Virus
- Danish boot
- Saturday the 14th
- Happy Birthday 30
Case-Study Based Questions
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?
- It locates infected files.
- It searches for the viruses.
- Once installed, it needs not be updated.
- It removes viruses.
(b) Which of the following is not an antivirus software?
- Google Chrome
(c) What is meant by pirated antivirus software?
- Copied from original software
- Reinstalled software
- Loaded from original CD
- None of the above
(d) What will happen if antivirus software is not updated periodically?
- It will be erased after some time.
- It will not be able to trace new viruses.
- It will force operating system to stop functioning.
(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
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.
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.
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.
Define Program Virus
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
What is a computer virus?
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.
Mention two ways of classifying a computer virus.
A computer virus can be classified into two categories based on their behaviour:
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.
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.
Name the different sources of virus from which it may enter to a computer system.
The different sources of virus 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 CD's.
- Browsing or downloading unwanted sites through the internet.
- Unwanted email attachments in the spam folder.
Why is it necessary to update antivirus software installed in your computer system?
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
Program Virus and Macro Virus
|Program Virus||Macro Virus|
|This virus directly attacks the program files of the system with the extension as .EXE, .SYS, .COM, .DLL, etc.||This virus attacks the data files of the system.|
|When a relevant task related to a program file is performed, it starts showing its destructive behaviour and the system fails to perform any task directly.||Whenever a user wants to work on any application package related to data files, he finds that either the file is destroyed or it contains some absurd data. Thus, the user is unable to perform any task on those data files.|
|For example- Sunday, Cascade etc.||For example- Bloodhound, Melissa|
Virus and Antivirus
|Computer virus is a malicious program, which has the ability to replicate and execute itself.||An antivirus software is a computer program used to scan files. It detects, prevents, identifies and eliminates computer viruses and other malicious softwares.|
|It is destructive in nature.||It is preventive in nature.|
|It harms the computer system in different ways.||It protects the computer system from viruses and other malicious softwares.|
Worms and Viruses
|A worm is a computer program that copies and multiplies itself by using computer networks and security flaws.||A virus is a malicious program which has the ability to execute and replicate itself.|
|A worm is self-sufficient i.e., it has the ability to spread itself without the use of another program or a user.||A virus attaches itself to other programs and spreads across the computer system.|
|Worms do not affect functioning of the system but interrupts services and drastically decrease the available memory of the system.||Once loaded, viruses start damaging the system by modifying information.|
Long Answer Questions
What are the various ways to get virus attack to a computer system?
The various ways to get virus attack to a computer system are:
- A virus infected floppy disk or other storage media like CD, DVD, pen drive can easily infect a system.
- Pirated softwares
- Hired computer games or audio or video CDs.
- Browsing unwanted websites through Internet.
- Unwanted mails in the spam folder.
How will you detect that a computer system is infected by viruses?
We can detect that a computer system is infected by viruses if we notice one or more of these 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.
State the various ways to protect your system from viruses.
We can protect our system against viruses by following these measures:
- Avoid using pirated CD/DVD to install any software in your system.
- If you are using a Pen drive to transfer data to your system, make sure that the drive is free from virus.
- If your system is connected to a LAN, keep a check on the users to avoid the misuse of the system.
- Don't browse unwanted websites.
- Install Antivirus software in your 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 e-mails while working with the e-mail account.
- Always keep a backup copy of your program/data files.
Why do people spread viruses? Explain.
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:
- They don't think about the consequences, others have to face.
- They draw a false distinction between creating/publishing viruses and distributing them.
- They consider it to be the responsibility of someone else to protect systems from their creations.
- This is a way they fight with the authorities.
- They think it is a way of getting attention/recognition from their peers.
- They want to engage the antivirus vendors in a job.
What is meant by an antivirus? Name different types of antivirus softwares.
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:
- Examining files to look for known viruses by means of a virus dictionary.
- 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.
You have loaded 'Norton Antivirus' software in your computer system. Does it make your computer system free from virus attack for a lifetime? Justify.
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.
What actions can an antivirus take, if a threat is detected in your computer system?
If a threat is detected in our computer system, our antivirus can take one or more of these actions in a specific order:
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.
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.
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.