A virus is a type of malware that attaches itself to programs, files, or boot sectors and spreads to other programs and systems. This malicious software is designed to replicate itself and spread from one system to another by injecting its code into other executable files and documents. Unlike other forms of malware, viruses require human intervention to propagate, such as opening a file or running an infected program.
Characteristics of a Virus
- Attachment: A virus attaches itself to legitimate programs or files.
- Replication: It copies itself to other programs or files once the infected program is executed or the infected file is opened.
- Activation: After replication, the virus activates to perform its destructive or payload-delivering actions.
- Spread: The virus spreads to other systems when the infected files or programs are transferred, such as through email attachments or network sharing.
Types of Viruses
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File Infector: Attaches itself to executable files. When these files run, the virus activates. Example: CIH virus, which corrupts data upon activation.
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Macro Virus: Embeds itself in documents containing macros, such as Word or Excel files. Example: Melissa virus, which spreads through infected email attachments.
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Boot Sector Virus: Infects the master boot record (MBR) of disks. It activates when the system starts up. Example: Michelangelo virus, notorious for activating on Michelangelo’s birthday.
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Polymorphic Virus: Changes its code each time it spreads to evade detection. Example: Storm Worm, known for changing its code to avoid antivirus detection.
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Multipartite Virus: Combines multiple infection methods, attacking both files and boot sectors. Example: Tequila virus, which uses file and boot sector infection methods.
Historical Context
The concept of a self-replicating computer program dates back to the early days of computing. The first acknowledged virus, the Creeper virus, was created in 1971 as an experimental self-duplicating program. However, it was the rise of personal computing in the 1980s that saw the proliferation of viruses as more malicious tools.
Applicability and Impact
Viruses can have severe implications, such as:
- Data Loss: Deleting or corrupting files.
- Resource Drain: Consuming system resources, slowing down the system.
- Unauthorized Access: Stealing sensitive information.
- Service Disruption: Causing systems to crash or become unavailable.
Comparisons with Other Malware
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Worms: Like viruses, worms replicate themselves but do not need human intervention to spread.
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Trojan Horses: Malicious programs disguised as legitimate software. They do not replicate like viruses.
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Ransomware: Encrypts files and demands ransom for decryption. It does not spread by attaching itself to other files.
Related Terms
- Antivirus Software: Programs designed to detect, prevent, and remove viruses and other malware.
- Malware: A broad category of malicious software, including viruses, worms, Trojans, ransomware, etc.
FAQs
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How can I protect my system from viruses?
- Use reputable antivirus software, keep your software up-to-date, avoid opening unknown email attachments, and avoid downloading software from untrusted sources.
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What should I do if my computer is infected by a virus?
- Run a full system antivirus scan, remove infected files, and restore your system from a clean backup.
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Can a virus infect a smartphone?
- Yes, smartphones can be infected by viruses, especially through apps and malicious downloads.
References
- “Computer Virus”, Wikipedia, The Free Encyclopedia.
- Security Intelligence, IBM.
- “The History of Computer Viruses”, Kaspersky.
Summary
A computer virus is a pernicious type of malware that attaches itself to legitimate programs or files and spreads to other systems. By understanding the various types, historical context, and impact of viruses, users can take educated precautions to protect their systems in the increasingly digital world.
