Antivirus PPt

Computer Virus

Arnab Singha, VI CSEVipin Borkar, VI CSE

1

What is a Computer Virus• A kind of software programs

– produced by unknown people and harmful

to the computers

• Some varieties of these software are the

– Viruses, Worms and Trojan horses

TitleWhat is a Computer Virus

• The term “Virus" is often commonly used

– to describe all kinds of malware (malicious

software)

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TitleDamages done by Viruses

• Sometimes display unwanted messages

• Some tend to destroy programs or data

• Clog computer memory and hence sometimes

result in system crashes

• Format hard disks, Damage programs, Delete

files

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Viruses

Damages done by Viruses

• Simply replicate themselves

• Presents text, video, or audio messages making the

user know their presence

• Bug-ridden, and these bugs may lead to system

crashes and data loss

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Virus spreading methods

• A viruses can copy itself and infect a computer

– without permission or knowledge of the user

• attaches itself to other software programs or

data files

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• Spreads from computer to computer when the

host is taken to the uninfected computer

– over a network such as over the Internet or carrying it

on a removable medium - a floppy disk, CD, or USB drive

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• Many viruses are existed in the Internet today

and new ones are discovered every day.

– spread via downloaded software and data files, and

email attachments, etc

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• Some old viruses are installed

themselves into the disk boot sector

– runs when the user boot the computer

from the disk

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• Some viruses spread through instant

messaging

– A virus, in an infected machine, may send a web-

address-link as a message to other contacting

machines

– Thinking the link is from a friend (a trusted source),

the recipient may sometimes follow the link to the

website.

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How Viruses are born?

• Unlike biological viruses, computer

viruses do not simply evolve by

themselves…

– deliberately created by programmers, or by

people who use virus creation software


• Viruses are written as

– research projects, pranks, vandalism,

– to attack the products of specific

companies,

– to distribute political messages,

– and financial gain from identity theft,

– spyware, and cryptoviral extortion. 12


• Some virus writers

– consider their creations to be works of art

– See virus writing as a creative hobby

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Releasing computer viruses is a crime in most jurisdictions

Viruses can avoid detection

• To avoid detection by users, viruses employ

different deception methods

– They do not make themselves to

• change the date of last modified

• increase file sizes

• damage the files

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– They kill the tasks associated with antivirus

software before it can detect them!!

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– They kill the tasks associated with antivirus

software before it can detect them

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How Antivirus software works?

• Use a heuristic algorithm to find viruses based

on common behaviors – Examin the content heuristics of the computer's

memory (its RAM, and boot sectors)

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• Some anti-virus programs gives you a

real time protection

– Examine files as they are being opened,

downloaded, copied, accessed, and

transmitted etc

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• They need regular updates

– in order to gain knowledge about the

latest threats

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Damage prevention & data recovering

• Take regular backups (including OS) on

different media, unconnected to the system

(most of the time)

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How to prevent damages caused by viruses?

Damage prevention & data recovering

• Use backups on optical media like CD and DVD

(read-only), as they can no longer be affected

by viruses.

• Use an OS on a bootable, to start the

computer if the installed OS become unusable.

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How to prevent damages caused by viruses?

Keep your computer Virus free

• Install reliable anti-virus software

– the most important step you can take towards keeping

your computer clean of viruses

• Update your anti-virus software regularly

– variations of viruses and new ones can be slipped if your

software is not current

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• Get immediate protection

– Configure your anti-virus software to boot automatically

on start-up and run at all times

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Don't automatically open attachments ensure that you examine and scan email and other

attachments before they run as they might contain

viruses

Scan all incoming email attachments Do not open any email attached files if the subject line is

questionable, unexpected or the source (address) is

unknown, suspicious or untrustworthy 24


• Delete chain emails and junk email

– Do not forward or reply to any of them, they clogs up

the network

– Some viruses can replicate themselves and spread

through email as a chain

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• Be careful when downloading files from the

Internet

– Ensure that the source is a legitimate and reputable one

– save all downloads to one folder and test them with your

own anti-virus software before use

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• Always scan new files for viruses before you

use them

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• Backup your files on a regular basis

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• If your computer is on a network, make sure

you have security steps in place to prevent

unauthorized users putting files on your

computer .

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• Take care using USB flash cards, CDs, zip and

floppy disks

– The more computers flash cards, CDs, zip cards and

floppies have been used on, the better the chance of a

virus infecting them – clean them before use

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Thank You

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Antivirus PPt