What Is virus in computer ? full explanation

 

A computer virus is a type of malicious software, or malware, designed to spread from one computer to another and interfere with computer operation. Much like a biological virus, a computer virus attaches itself to a host file or system and requires user interaction to spread, often unbeknownst to the user. Here's a comprehensive explanation of what a computer virus is, how it works, its types, and methods of prevention and removal.

 Definition and Characteristics

A computer virus is a self-replicating program that can infect other programs or files by modifying them and inserting its own code. Key characteristics include:

- **Self-replication**: Viruses can copy themselves and spread to other files and systems.

- **Malicious intent**: They often cause harm, ranging from corrupting data to taking control of system resources.

- **Trigger mechanism**: Many viruses are designed to execute their payload (malicious activity) when specific conditions are met, such as a particular date or action by the user.

How Computer Viruses Work

1. **Infection**: A virus attaches itself to a legitimate file or program, such as executable files (.exe), scripts, documents, or other types of data files. It can also be embedded in the boot sector of a disk or included in software downloads.

2. **Activation**: Once the infected file is executed or the system is booted from an infected disk, the virus is activated. 

3. **Replication**: The virus replicates itself by modifying other files or programs and inserting its own code. This can happen in various ways, such as attaching to files, embedding in macros, or modifying system sectors.

4. **Payload Delivery**: When specific conditions are met, the virus executes its payload. This can include actions like deleting files, stealing data, displaying messages, or using system resources for malicious activities.

Types of Computer Viruses

1. **File Infectors**: These viruses attach themselves to executable files. When the infected program is run, the virus is activated. Examples include the CIH virus and the Cascade virus.

2. **Boot Sector Viruses**: These infect the master boot record (MBR) of a hard drive or the boot sector of a removable storage device. They are loaded into memory during the boot process. Examples include the Michelangelo and Stoned viruses.

3. **Macro Viruses**: These viruses infect documents that contain macros, such as those created in Microsoft Word or Excel. When the document is opened, the macro virus executes. Examples include the Melissa and Concept viruses.

4. **Polymorphic Viruses**: These viruses can change their code slightly each time they replicate, making them harder to detect by antivirus programs. Examples include the Storm Worm and the Marburg virus.

5. **Resident Viruses**: These viruses embed themselves in the system's memory and can infect files as they are accessed by the system or other programs. Examples include the Randex and CMJ viruses.

6. **Non-resident Viruses**: These viruses do not embed themselves in memory but instead infect files directly when executed. Examples include the Vienna and Cascade viruses.

 Spread and Infection Vectors

- **Email Attachments**: Malicious attachments in emails can infect systems when opened.

- **Infected Software Downloads**: Downloading and installing software from untrusted sources can introduce viruses.

- **Removable Media**: USB drives, external hard drives, and other removable media can carry viruses from one system to another.

- **Network Connections**: Infected systems on a network can spread viruses to other connected devices.

- **Exploits and Vulnerabilities**: Viruses can exploit security vulnerabilities in software to infect systems without direct user interaction.

Prevention and Protection

1. **Antivirus Software**: Install and regularly update antivirus programs to detect and remove viruses.

2. **Regular Updates**: Keep operating systems and software up to date with the latest security patches.

3. **Email Security**: Be cautious with email attachments and links, especially from unknown senders.

4. **Safe Browsing**: Avoid downloading software from untrusted websites and clicking on suspicious links.

5. **Firewalls**: Use firewalls to monitor and control incoming and outgoing network traffic.

6. **Backup Data**: Regularly back up important data to recover from potential virus infections without significant loss.

 Detection and Removal

- **Antivirus Scans**: Run regular scans using antivirus software to detect and remove viruses.

- **System Restore**: Use system restore points to revert the system to a previous state before infection.

- **Manual Removal**: For advanced users, manually identifying and deleting infected files or using specialized removal tools can be effective.

- **Professional Help**: In severe cases, seeking professional assistance from IT experts may be necessary to fully remove the infection and secure the system.

In conclusion, computer viruses are a significant threat to digital security, capable of causing extensive damage and disruption. Understanding their nature, modes of operation, and protective measures is essential for maintaining a secure computing environment.

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