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What is virus state the various types of virus and the basis in which they are classified

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A computer virus is a type of malicious software that can replicate itself and spread to other computers or files, often with the intent of causing harm to the system or stealing information. Viruses can attach themselves to legitimate programs or documents and execute malicious code when the infected file is opened or executed.

Viruses are classified based on various criteria, including their behavior, propagation methods, and payload. Here are some common types of computer viruses and their classifications:

  1. File Infector Viruses:

    • Description: These viruses attach themselves to executable files and may spread when the infected file is executed.
    • Examples: CIH, Sasser, and Nimda.
  2. Boot Sector Viruses:

    • Description: These viruses infect the master boot record (MBR) of a storage device, making them active during the system boot process.
    • Examples: Stoned, Michelangelo.
  3. Macro Viruses:

    • Description: Macro viruses infect macro language scripts, often embedded in documents (e.g., Microsoft Word or Excel files).
    • Examples: Melissa, Concept.
  4. Polymorphic Viruses:

    • Description: Polymorphic viruses change their appearance each time they infect a new file or system, making detection more challenging.
    • Examples: Storm Worm, Marburg.
  5. Metamorphic Viruses:

    • Description: Similar to polymorphic viruses, metamorphic viruses can change their code entirely, making it more difficult for antivirus programs to identify them.
    • Examples: ZMist, Simile.
  6. Multipartite Viruses:

    • Description: Multipartite viruses use multiple infection methods, combining features of file infectors, boot sector viruses, and more.
    • Examples: Tequila, Invader.
  7. Resident Viruses:

    • Description: Resident viruses embed themselves in the computer's memory and can infect files as they are opened, closed, or executed.
    • Examples: Randex, CMJ.
  8. Non-Resident Viruses:

    • Description: Non-resident viruses do not stay in the computer's memory after the infected file is closed or the system is restarted.
    • Examples: Cascade, Vienna.
  9. Worms:

    • Description: While not technically viruses, worms are self-replicating programs that spread across networks, exploiting vulnerabilities to infect other computers.
    • Examples: Code Red, Conficker.
  10. Trojan Horses:

  • Description: Trojan horses disguise themselves as legitimate programs or files but carry malicious payloads that can harm the system or steal information.
  • Examples: Sub7, Zeus.

These classifications are not mutually exclusive, and some viruses may exhibit characteristics of multiple types. As technology evolves, new types of viruses and malware continue to emerge, prompting ongoing efforts to develop effective cybersecurity measures.

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