It is called a computer virus, any program that can infect other programs by modifying them to include themselves within these programs.
It seems that the first computer virus was conceived on November 3, 1983, as an experiment presented in an IT Security weekly seminar. The virus was shown on November 10, the same year after obtaining the necessary authorizations and completing five experiments.
One of the major contributions in this study was to clarify the fact that no virus scanner is perfect, in the sense that it allow us a 100% clear verification mechanism to decide whether a given program meets or not the conditions for consider it as a virus.
This is how it’s explained the endless fight between viruses and antiviruses, whose patterns are marked by the same trends in the evolution of technology and its impact on the ways that are given in the creation of the malicious codes. However, thanks to the fact that there is a fairly solid support for this issue, it is how nowadays it is quite simple to create almost immediately solutions for the various new viruses that show up.
Until the eighties, the term virus ( which means poison in Latin ), it was only used within the medical and biological sciences fields to describe the microorganisms capable to penetrate the human beings and destroy or alter the genetic cellular content causing various pathological conditions. It is because of the certain similarities of the way of action and characteristics of its effects, were certain programs named computer viruses, programs that can reproduce themselves (“transmitting themselves” from one computer to another, and causing damage to information and the system itself).
Until recently, most of the viruses were only programmed in the assembly language, but with the undeniable progress of the 32-bit operating systems, Internet and email, the combination between the assembly language and other languages is a growing idea. This, because the natural tendency is to guide the world of viruses towards hacking, enabling the possibility of the virus to steal the password files of a computer and achieving its per-establish illegitimate email sending, highlighting the extreme insecurity of today's operating systems.