**Description:** A computer virus is a type of malware that attaches itself to legitimate programs and can spread to other computers. Its main characteristic is the ability to replicate, allowing it to infect other files and systems. Viruses can be designed to perform various malicious actions, such as stealing information, damaging files, or even taking control of the affected system. They often activate when the user runs the infected program, triggering the virus’s spread. Computer viruses can be difficult to detect, as they often disguise themselves as legitimate software and may remain dormant for a time before activating. Prevention and detection of viruses are crucial in cybersecurity, and various tools, such as antivirus software and firewalls, are used to protect systems from these threats.
**History:** The first known computer virus, called ‘Creeper’, was created in 1971 by Bob Thomas as an experiment on the ARPANET network. However, the first virus to effectively spread was ‘Elk Cloner’, created in 1982 by a high school student named Rich Skrenta. Over the years, viruses have evolved in complexity and sophistication, with notable examples such as the ‘Melissa’ virus in 1999 and ‘ILOVEYOU’ in 2000, which wreaked havoc worldwide. The antivirus software industry has also grown in response to this threat, developing tools to detect and remove viruses.
**Uses:** Computer viruses are primarily used to cause damage to computer systems, steal sensitive information, or disrupt the normal functioning of a network. Some viruses are designed to perform denial-of-service (DoS) attacks, while others can be used to create botnets, which are networks of infected computers controlled by an attacker. They can also be used to propagate other types of malware, such as ransomware, which encrypts a user’s files and demands a ransom for their release.
**Examples:** Examples of computer viruses include ‘Melissa’, which spread through Word documents in 1999, and ‘ILOVEYOU’, which was distributed as an email with a malicious attachment in 2000. Another example is the ‘Mydoom’ virus, which became one of the fastest-spreading viruses in history, affecting millions of computers in 2004. These viruses not only caused damage to systems but also generated significant economic losses.
