A virus is a program that “infects” computers and acts like malicious code. The virus has the ability to replicate itself many times and thereby spread throughout the system. These programs usually attack files of specific applications, as well as files with a specific extension.
Infection of a computer, as a rule, occurs through penetration into executable files, the virus can also attack data files, for example, graphic, text, etc. However, in the latter case, the activity of the virus depends on the application to which the file belongs.
The varieties of viruses are the so-called worms and trojans. Unlike ordinary viruses, they do not penetrate directly into the file code, but act autonomously, while copying themselves many times. Worms are used to spread spam and viruses on local networks or the Internet. A Trojan is a program designed to steal personal data or remotely intercept control with subsequent use of the computer, for example, in DDos attacks.
There is no clear distinction between viruses by the type of their action. In most cases, a virus means any code that performs malicious actions without the user's knowledge. However, viruses do not include programs that, on the one hand, constantly issue advertising messages or redirect the user to certain sites, and on the other, cannot be launched without the direct consent of the user himself. Such programs usually require confirmation of the license agreement before they can be installed, so their actions cannot be considered malicious.
