Types of Viruses

A computer virus is a type of malicious code that enters the system along with files or programs and carries out malfunctions in the system. The virus-affected program becomes a replica of the existing program. They enter the system through files and when the file runs, the virus also runs in the background.

Viruses infiltrate systems through various methods including email attachments, clicking malicious advertisements, and downloading software from unauthorized websites. Their main objective is to spread across different hosts while stealing personal data and system credentials.

Types of Computer Viruses

A virus is a specific type of malware, though not all malware are viruses. Common examples include Nimda, Trojan, Tinba, SQL Slammer, and CryptoLocker. Here are the main types of viruses that affect computer systems:

Boot Sector Virus

Boot sector viruses enter the system through USB drives and affect storage sectors containing startup folders. They insert malicious code into the startup folder and execute during the operating system's boot process, running before security software like antivirus programs can start.

These viruses affect the system during startup and can damage it completely. Modern operating systems like BIOS and UEFI have preinstalled security measures against boot sector viruses.

Examples Elk Cloner, Brain, Stoned, and Parity Boot

Parasitic Virus

Parasitic viruses attack files with .exe or .com extensions, spreading by attaching themselves to other programs. Also called file viruses, they hide within files and run alongside the host program. Users can avoid these viruses by not clicking suspicious links.

Examples Virut, Sality, and Vetor

Stealth Virus

Stealth viruses hide inside files within the operating system, remaining undetectable to users. They steal data, change encryption, and modify their own code. These viruses typically hide in the boot section and require updated, robust antivirus software for detection and removal.

Example Brain

Macro Virus

Macro viruses are coded in macro language, primarily used for designing software applications. They affect software applications regardless of the operating system, exploiting the shared macro language between the application and virus.

Examples Melissa and Nuclear

Polymorphic Virus

Polymorphic viruses enter machines through infected systems, corrupted files, and emails. They have complex structures that make detection difficult, modifying themselves according to the target software while affecting data and functions.

Examples VIRLOCK, VOBFUS, and BAGLE

Source Code Virus

Source code viruses modify the infected computer's source code directly. These rare viruses are extremely difficult to remove once they hijack and corrupt the machine's core programming.

Resident Virus

Resident viruses target the computer system's memory files and are considered among the worst because they attach to antivirus software files, corrupting the security programs themselves.

Examples Meve, CMJ, and Randex

Tunneling Virus

Tunneling viruses detect when antivirus software identifies them as malicious. They then infiltrate the antivirus program, intercept its functions, and prevent the security software from running effectively.

Example Frodo

Multipartite Virus

Multipartite viruses are among the fastest-spreading viruses, simultaneously affecting executable files and system boot sectors. They target multiple system components including memory and the operating system.

Examples Invader and Flip

Virus Prevention Strategies

Conclusion

Computer viruses represent a significant cybersecurity threat with various types targeting different system components. Understanding these virus categories helps implement appropriate security measures including updated antivirus software, safe browsing practices, and regular system monitoring to protect against malicious attacks.