Computer Virus

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Computer Virus
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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

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What is a Computer Virus

• The term Virus" is often used in common
• to describe all kinds of malware (malicious
  software)

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Damages done by Viruses
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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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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Virus spreading methods

• 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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Virus spreading methods

• 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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Virus spreading methods

• 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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Virus spreading methods

• 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 websit.

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How Viruses are borne

• Unlike biological viruses, computer viruses do
  not simply evolve by themselves
• deliberately created by programmers, or by people
  who use virus creation software

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How Viruses are borne

• 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.

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How Viruses are borne

• Some virus writers
• consider their creations to be works of art
• See virus writing as a creative hobby

Releasing computer viruses is a crime in most
jurisdictions
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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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Viruses can avoid detection

• They kill the tasks associated with antivirus
  software before it can detect them

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How Antivirus software works?

• Detect using a list of virus signature
  definitions
• comparing the files stored on fixed or removable
  drives (hard drives, floppy drives), against a
  database of known virus "signatures".

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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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How Antivirus software works?

• Some anti-virus programs gives you a real time
  protection
• Examin files as they are being opened,
  downloaded, copied, accessed, and transmitted etc

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How Antivirus software works?

• They need regular updates
• in order to gain knowledge about the latest
  threats

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Damage prevention data recovering
How to prevent damages caused by viruses?

• Take regular backups (including OS) on different
  media, unconnected to the system (most of the
  time)

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Damage prevention data recovering
How to prevent damages caused by viruses?

• 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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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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Keep your computer Virus free

• Get immediate protection
• Configure your anti-virus software to boot
  automatically on start-up and run at all times

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Keep your computer Virus free

• 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

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Keep your computer Virus free

• 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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Keep your computer Virus free

• 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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Keep your computer Virus free

• Always scan new files for viruses before you use
  them

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Keep your computer Virus free

• Backup your files on a regular basis

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Keep your computer Virus free

• 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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Keep your computer Virus free

• 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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