Easy to Understand Guide to Computer Viruses

What is a Computer Virus?

A computer virus is a type of computer program that can copy itself and gravely infect a computer system. Although the term “virus” is commonly attached to other types of malicious software, including forms of adware and spyware programs, they are technically held separate because forms of malware do not possess a reproductive ability.

A traditional computer virus has the ability to spread from one computer system to another. The transfer is accomplished through some form of executable code. The spread of a computer virus occurs when its host is taken to the target computer. To spread, the computer virus needs some form of medium, such as a network or the Internet. In addition, a computer virus may be carried on a removable medium, such as a CD, DVD, floppy disk, or a USB drive.

Difference between a Computer Virus and Malware

The term “computer virus” is often used as a catch-all phrase to include various types of malicious software, even those that do not possess a reproductive ability. This definition, however, is categorically incorrect for malicious software or malware is a broader term that includes computer worms, Trojan horses, dishonest adware, spyware, and true viruses.

Although a computer virus, a Trojan horse and worms share the same destructive characteristics, these forms of malicious hardware are technically different. A worm exploits a platform’s security vulnerabilities and will spread automatically to other systems through the network, while a Trojan horse is a separate program that appears harmless, but hides malicious software. As a result, worms and Trojan horses, like a computer virus, will harm a computer system’s performance.

How does a Computer Virus Work?

In order for a computer virus to replicate itself, it must be permitted to execute code and write memory in the system’s database. To accomplish these functions, a computer virus may attach itself to executable files that may appear or be a part of legitimate programs. If the user attempts to access or launch a program that is infected, the virus’ code may be executed.

A computer virus may be divided into classifications based on their behavior when executed. A nonresident computer virus, when executed, will immediately search for other hosts that can be infected. When this occurs, the computer virus infects the targets and transfers control to the application program.

A resident virus will not search for hosts when they are executed, but instead, load itself into memory and subsequently transfer control to the host program. The resident virus stays active in the background and infects new hosts when the attached files are accessed by other programs or by the operating system itself. A resident virus contains a replication module, which is almost a replica to the one that is executed by the nonresident virus. The virus loads the replication module into the system’s memory when executed. The module is then subsequently executed each time the system is asked to perform a specific operation.

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