What is virus? Types and it's function.

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 A computer virus is malicious software designed to disrupt, damage, or gain unauthorized access to computer systems. These viruses attach themselves to files or programs, replicate, and spread across systems, affecting performance, corrupting data, and even stealing information. Here are some common types of computer viruses, along with examples of each.

Types of Computer Viruses and Examples

  1. File Infector Virus:

    • Description: Attaches itself to executable files (such as .exe or .com files). When an infected file runs, the virus activates and can infect other files on the system.
    • Examples:
      • Cascade Virus: Causes text in files to cascade or "fall down" on the screen.
      • Sunday Virus: Activates on certain days to corrupt or delete files.

  2. Macro Virus:

    • Description: Targets documents that support macros, such as those created in Microsoft Word or Excel. Activates when a user opens an infected document, allowing it to spread through shared files.
    • Examples:
      • Melissa Virus: Spreads through infected Word documents sent via email, auto-sending to contacts in a user’s email address book.
      • Concept Virus: One of the first macro viruses, targeting Microsoft Word and spreading through infected documents.

  3. Boot Sector Virus:

    • Description: Infects the boot sector of hard drives or USB drives, containing the code needed to start a computer. Activates when the computer boots, often before antivirus software loads.
    • Examples:
      • Stone Virus: Spread via floppy disks, affecting the boot sector.
      • Disk Killer: Infected boot sectors and could cause potential system failures.

  4. Polymorphic Virus:

    • Description: A polymorphic virus changes its code each time it infects, making it difficult for antivirus software to detect.
    • Examples:
      • Storm Worm: A highly polymorphic virus that spread through malicious email attachments.
      • CryptoLocker: This ransomware polymorphic virus encrypts files and demands a ransom to unlock them.

  5. Resident Virus:

    • Description: Resides in a computer’s memory and activates whenever the operating system executes certain functions. It doesn’t need to attach to specific files to spread, so it can remain hidden.
    • Examples:
      • Randex Virus: Created backdoors in infected computers, allowing unauthorized access.
      • CMJ Virus: Causes system slowdowns and interrupts normal operations.

  6. Multipartite Virus:

    • Description: Infects both the boot sector and executable files, spreading in multiple ways and impacting different parts of a system.
    • Examples:
      • Invader Virus: Infects both files and boot sectors, making it resilient to traditional removal.
      • Flip Virus: A multipartite virus that infected boot sectors and files, allowing it to spread in more than one way.

Functions of Computer Viruses

  1. Data Destruction: Some viruses are designed to delete, alter, or corrupt essential files and data.
  2. System Performance Slowdown: Viruses consume a computer’s processing power and memory, slowing down system performance.
  3. Unauthorized Data Access: Certain viruses collect sensitive data, like personal information, bank details, and passwords.
  4. Replication and Spread: Viruses replicate themselves, aiming to infect as many files and systems as possible, often spreading through emails, links, or removable devices.
  5. Display of Pop-ups and Advertisements: Adware-type viruses display unwanted advertisements, redirecting users to harmful or fraudulent websites.

Protecting Against Computer Viruses

  1. Install Antivirus Software: Antivirus software detects and removes viruses before they cause harm.
  2. Regular Software Updates: Updating software and the operating system ensures that you have the latest security patches.
  3. Avoid Suspicious Downloads and Links: Don’t download files or click on links from unknown sources.
  4. Back Up Important Data: Regular backups prevent data loss in case a virus corrupts files.

Taking these preventive steps reduces the risk of virus infections on your computer.





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