Computer viruses come in many forms, each with different infection methods and effects. Understanding the types of viruses helps in recognising threats and choosing appropriate protection. This knowledge is part of the CBSE Class 7 computer security curriculum.
File infector viruses attach themselves to executable files (.exe, .com, .bat). When the infected file is run, the virus activates and can spread to other executable files on the system. These are among the most common types of viruses. Examples include the Cascade virus and the Sunday virus.
Boot sector viruses infect the Master Boot Record (MBR) of a hard disk or the boot sector of floppy disks and USB drives. They activate when the computer starts up (boots), even before the operating system loads. They were very common in the floppy disk era. Examples include the Brain virus (the first known PC virus) and the Stone virus.
Macro viruses target applications that use macros, such as Microsoft Word, Excel, and PowerPoint. They embed malicious code in the macro instructions of documents. When an infected document is opened, the macro virus executes. The Melissa virus (transmitted via email as a Word document) is a famous example.
A Trojan horse (or Trojan) disguises itself as a useful or harmless program to trick users into installing it. Unlike viruses or worms, Trojans do not replicate themselves. Once installed, they can create backdoors for hackers, steal data, or install additional malware. They are named after the ancient Greek story of the wooden horse of Troy.
Though technically not viruses, worms are often discussed alongside them. Worms are self-replicating programs that spread over networks without user intervention. They exploit security vulnerabilities to move from computer to computer. The Code Red worm and WannaCry ransomware (which combined worm-like spreading with encryption) are notable examples.
Protection strategies include: (1) Install reputable anti-virus software and keep it updated. (2) Keep your operating system patched with the latest security updates. (3) Be cautious with email attachments and downloads. (4) Enable macro security in office applications. (5) Use a firewall. (6) Regularly back up important data. (7) Disable autorun for USB devices.
The Brain virus (1986) is considered the first computer virus for IBM PCs. It was a boot sector virus created by two Pakistani brothers to protect their medical software from piracy.
Yes. Smartphones can be infected by malware through malicious apps, phishing links, and infected websites. Using an app store and keeping the OS updated reduces risk.
No. A Trojan disguises itself as legitimate software but does not replicate. A virus attaches to files and replicates by infecting other files. Both are types of malware but operate differently.
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