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  • A potentially damaging computer program capable of reproducing itself causing great harm to files or other programs without permission or knowledge of the user.
  • Computer viruses are perceived as a threat to both business and personnel
  • Virus is a self-replicating program that produces its own code by attaching copies of itself into other executable codes
  • Operates without the knowledge or desire of the computer user

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  • Computer viruses are a type of software program that, like a biological virus, reproduces and spreads itself
  • Some virus may display only a message on the screen, others may slow down the Pc
  • They can also erase files or even format your floppy or hard disk and crash the system.

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Who creates/writes viruses ?

  • Gather information about the destination or host. This provides huge money for the attackers by gathering the information like bank details or any other confidential informations.
  • Virus/Antivirus market - It’s a high end potential business in the field of antivirus. Many antivirus companies are making billions of money in this field or removing virus.


  • For Fun - To make fun on others, hackers will attack the victims.
  • To Take Revenge on others
  • To show Anger by attacking the victims / opponents

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Characteristics of a Virus

  • The virus will resides in the memory and replicates itself while the program where it attached, is running May or May not - Does not reside in the memory after the execution of program Can transform themselves by changing codes to appear different Hides itself from detection by three ways:
    • Encrypted Viruses - Encrypts itself into cryptic symbols
    • Memory consuming virus - Alters the disk directory data to compensate the additional virus bytes
    • Corrupt disk data - Uses stealth algorithms to redirect disk data

The functional logic of a Virus

  • Search for a file to infect.
  • Open the file to see if it is infected.
  • If infected, search for another file.
  • Else, infect the file.
  • Return control to the host program.

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Virus Propagation


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Prevention & cure of computer viruses

  • Install an Antivirus software
  • Regularly update the program
  • Open email attachment files only if you are expecting the attached files, or the sender is known and has confirmed sending the file
  • Try to avoid downloading and installing software from the Internet
  • Install only registered copies of software on the system

Removal of Some Common Viruses

  • We can remove some of the common viruses without help of any antivirus Program.
  • e.g.- New Folder.exe, Autorun.inf

New Folder.exe

  • It looks just like an folder but actually it is a .exe file.
  • Try to deleting the file.
  • It will delete if you haven’t executed it, if you’re unable to delete it.
  • Go to Task manager ( by pressing ctrl+shift+del )

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  • Go to Process Tab and try finding that the process for
  • the exe file and end the process.
  • Then Go to the same folder containing the exe file and
  • delete it.
  • Then Open Search and try finding the .exe files of same
  • size and delete them all.

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Removal of Autorun.inf

  • Open Run dialog Box. Type in “CMD” press ENTER.

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  • The Command Prompt will Open Now. In Command prompt go to the drive containing Autorun.inf
    • Now Type In “ attrib -h -s -a” and press enter

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  • This will remove drives attributes for all Hidden, System files.
  • Now Type “ Del autorun.inf” and press ENTER.
  • The Virus has been Successfully Removed

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