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COMPUTERCOMPUTER **VIRUSVIRUS * *

Compiled ByCompiled By::

Sanmitha Rao Sanmitha Rao B.Sc 4B.Sc 4thth sem sem

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CONTENTSCONTENTS IntroductionIntroduction Origin of VirusesOrigin of Viruses Symptoms of virus attackSymptoms of virus attack General Virus TypesGeneral Virus Types Prevention is the best curePrevention is the best cure Working of antivirus softwareWorking of antivirus software Practice safe ComputingPractice safe Computing

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What is a virus?What is a virus? Virus is a Virus is a Computer programComputer program like any other like any other

ProgramProgram It gives Instructions to your computer to do It gives Instructions to your computer to do

the things which you don’t want it to do.the things which you don’t want it to do. It It spreadsspreads.. It can be destructive.It can be destructive. It could format your hard drive boot sector It could format your hard drive boot sector

or delete your files and render your or delete your files and render your machine inoperable.machine inoperable.

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*ORIGIN*ORIGIN * *

People normally create viruses People normally create viruses by writing a code .by writing a code .

Generally people create viruses Generally people create viruses just for thrill or fun.just for thrill or fun.

In early days viruses were pieces In early days viruses were pieces of code attached to a program.of code attached to a program.

There are estimated 30,000 There are estimated 30,000 viruses, over 300 viruses are viruses, over 300 viruses are created each month.created each month.

First virus was created to show First virus was created to show loopholes in software.loopholes in software.

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Symptoms of Virus attackSymptoms of Virus attackSymptoms of Virus attackSymptoms of Virus attack

Computer runs slower than usualComputer runs slower than usual Computer no longer boots upComputer no longer boots up Screen sometimes flickerScreen sometimes flicker PC speaker beeps periodicallyPC speaker beeps periodically System crashes for no reasonSystem crashes for no reason Files /directories sometimes disappearFiles /directories sometimes disappear Denial of Service (Dos)Denial of Service (Dos)

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TYPES OF VIRUSESTYPES OF VIRUSES

1.1. Boot Sector VirusBoot Sector Virus

2.2. Macro VirusMacro Virus

3.3. Multipartite VirusMultipartite Virus

4.4. Polymorphic VirusPolymorphic Virus

5.5. E-mail VirusesE-mail Viruses

6.6. WormsWorms

7.7. Trojan horses etc.Trojan horses etc.

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Traditional VirusTraditional Virus Infect the boot on floppy disks and hard Infect the boot on floppy disks and hard

disks.disks. By putting its code in the boot sector virus By putting its code in the boot sector virus

can guarantee it gets executed.can guarantee it gets executed. Load itself into the memory and it is able Load itself into the memory and it is able

to run whenever the computer is on.to run whenever the computer is on.

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Written using a simplified Written using a simplified programming language these viruses programming language these viruses can effect your Microsoft applications can effect your Microsoft applications like word and excel like word and excel

A document infected with the Macro A document infected with the Macro Virus generally modifies a pre-Virus generally modifies a pre-existing commonly used command existing commonly used command (such as save) to trigger its payload (such as save) to trigger its payload upon execution of that command.upon execution of that command.

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This can infect both your files This can infect both your files and boot sectorand boot sector

It can infect thousands of times It can infect thousands of times to your system before it is to your system before it is caught.caught.

It is a dangerous virus.It is a dangerous virus.

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Changes code whenever it Changes code whenever it passes to another passes to another machine.machine.

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It moves around in the email It moves around in the email messages.messages.

Usually replicates itself by Usually replicates itself by automatically mailing itself to the automatically mailing itself to the dozens of people in the victims e-dozens of people in the victims e-mail address book.mail address book.

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It has the ability to copy itself It has the ability to copy itself from machine to machine.from machine to machine.

Eat up storage space and Eat up storage space and slows down the computer.slows down the computer.

Normally move around and Normally move around and infect other machine through infect other machine through computer networks.computer networks.

But worms don’t alter or But worms don’t alter or delete files.delete files.

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It is basically a computer program It is basically a computer program that claims to do one thing, but that claims to do one thing, but instead it damages the computer.instead it damages the computer.

It can It can capture information from capture information from your systemyour system such as user name such as user name and password or and password or could allow a could allow a malicious hacker to remotely malicious hacker to remotely control yourcontrol your system. system.

It has no way to replicate It has no way to replicate automatically.automatically.

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PREVENTION IS THE BEST PREVENTION IS THE BEST CURECURE

1.1. Install a virus protection software.Install a virus protection software.2.2. Run a secure operating system like Unix or NT.Run a secure operating system like Unix or NT.3.3. Avoid programs from unknown sources.Avoid programs from unknown sources.4.4. Disable floppy disk booting.Disable floppy disk booting.5.5. Macro virus protection is enabled in all Microsoft Macro virus protection is enabled in all Microsoft

applications.applications.6.6. Never double click on the attachment that comes as an Never double click on the attachment that comes as an

executable that arrives as an email attachmentexecutable that arrives as an email attachment..

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Working of Antivirus SoftwareWorking of Antivirus Software There are two ways in which a There are two ways in which a

antivirus software works-scanning antivirus software works-scanning software kooks for a software kooks for a virus,scanning software looks for virus,scanning software looks for a unusual virus.a unusual virus.

For a known virus software will For a known virus software will look for a virus signature and will look for a virus signature and will zap it from the system.zap it from the system.

For an unknown virus the For an unknown virus the software quarantines the software quarantines the questionable program and will questionable program and will inform you about what the inform you about what the program may be trying to do.program may be trying to do.