Computer Chap 7 - Computer Virus

7 Computer Virus

Que 1.  Wht is a Computer Virus?

Ans :-    A computer virus  is a program which is loaded onto your computer without your knowledge and cause interferences  with computer operation.

Que 2.  What are the symptoms 0f a Computer Virus? Or

              How do you find out if your computer is infected with a virus?

Ans :-   if your computer is infected with a virus it shows the following signs:

ÒFunctions slower than normal.

ÒResponds slowly and freezes often.

ÒFiles or folders gets deleted or changed without the user knowledge.

ÒSee uncommon error messages, distorted menus, and dialog boxes.

ÒNotice applications fail to work correctly.

ÒHard disk may get erased.

ÒFiles become bigger in size, thereby reducing disk space

Que 3.  Explain different types of computer viruses in detail:

Ans:- Computer viruses can be classified into different types based on their origin, techniques, the types of files they infect, the kind of damage they cause and the platform they attack.

The main type of computer viruses are:

1) File Virus :-   File virus infects program files such as .exe. .com etc. Once this virus gets active in the memory, it tries to infect all the programs that are further loaded into the memory.

2) Macro Virus :- It is a type of virus which infects the Microsoft Word and other applications. Once infected repairing these files become very difficult.

3) Boot sector or Master Boot Record(MBR) Virus:- This kind of virus infects the first sector of a storage device which is used for loading the operating system. It becomes active as soon as the computer is started.

4) Multipartite Virus :- It is a combination of Boot and Program/file viruses. It infects program files and when an infected program is executed, the virus infects the boot record. When the computer is booted the next time the virus from the boot record loads into the memory and then it starts infecting other program files on the disk as well.

5) Polymorphic Viruses :- A polymorphic virus is a self-encrypted virus designed to avoid detection by a scanner. Upon infection, the polymorphic virus duplicates itself by creating usable, albeit slightly modified, copies of itself.

6) Worms :- These kind of virus makes copies of itself and spread to other computer through network thereby showing down the traffic on the network. Able to  spread very quickly makes them really damaging. For ex. Blaster, Code Red and Sasser.

7) Trojan Horse :- Not considered as virus as it cannot replicate itself. A Trojan horse is a coded program which makes the existence of a virus by making its appearance look normal while containing malicious utilities transparent to the user. It may creates breaks in the security of the system by leaking information through a backdoor. Generally used for online  fraud and theft of confidential and personal data. For ex.  ‘Waterfall.scr’, ‘Beast’

Que 4.  How to protect your computer from viruses?

ÒUpload and use antivirus software

ÒBe aware of the e-mails and attachments you open

ÒCheck for updates on antivirus software regularly

ÒMake sure antivirus software is installed correctly

ÒEnable the Macro Virus Protection in MS Office application and do not run macros unless you know what they do.

ÒUse email programs that have built in spam filters.

ÒAvoid installing programs from unknown sources.

ÒAlways keep a regular back up of the your data to avoid any loss  

Que 5.  What is the use of Anti-Viruses Software?

Ans:- Anti-Virus Software scans files on your computer and the computer memory for known viruses.

Que 5.  How does  Anti-Viruses Software work?

Ans:- if the Anti-Virus program finds a virus, it may attempt to

§  Remove the virus(clean the file),

§  Quarantine the files(move the file to a safe area so that it cannot harm your system),

§  Delete the file.

Since new viruses are being released continually, the Anti-virus software needs to updated on a regular basis to that you have the least definitions installed in your computer.

Que 6.  Give few examples of Anti-virus Software.

§  AVG

§  BitDefemder

§  Kaspersky

§  AcAfee

§  Norton

§  Quick Heal

Que 7. Fill in the Blanks.

1) A Boot Sector virus infects the first sector of a storage device which is used for loading OS programs.

2) ‘Waterfall.scr’ is an example of a Trojan horse.

3)  Anti-virus software needs to be updated to keep track of latest viruses.

4) Quarantine is a term used to move an infected file to a safe area to that it cannot harm your system.

5) ‘Code Red’ and ‘Sasser’ are example of worms.

6) The Melissa virus or (1999) forced MS to temporarily shut down its email servers.

7) The I Love You virus(2000) came as an email attachment which on double clicking sent copies of it to everyone on the victim’s address book.

8) Code Red made headlines(2011) when it slowed down internet traffic by replicating itself.