What is a computer virus?

Beginners who have just started to master the world of computer technology are often asked on forums about what a computer virus is. Now such communities are available to everyone, just type the words in the browser search bar. Nevertheless, there are often users who absolutely do not know what a computer virus is. Moreover, such people are a source of dangerous delusions, mistaken themselves, informing others of the wrong information. In this work we will try to understand in clear language what a computer virus is, and to separate the "grains from the chaff".

Viruses are small programs that often have the ability to clone (multiply) themselves and perform tasks that are unfit for the computer owner.

From this definition, you can derive a number of consequences and more accurately determine what a computer virus is:

- All of them always (in one way or another) hide the fact of their presence. Otherwise, you can simply delete them (disable performance).

- Any media that has direct access to the file system (hard drive, flash drive), being connected to an infected computer, becomes potentially dangerous for "clean" systems, as the virus clones itself onto it.

- The virus is not something ephemeral, but the most common program, so it can be indirectly or directly detected and equipped with special tools. In addition, for obvious reasons, viruses written for a certain environment (DOS, Windows, Linux) do not work in the other.

- Any actions performed without the user's knowledge are objectionable. And since viruses are often created to steal confidential data, it is also malicious.

In principle, to understand this is quite enough. To understand more, you need to familiarize yourself with what types of viruses there are.

The species is determined by the tasks of the virus. At present, there are tens of thousands of such malicious programs. The tasks pursued by the first virus writers are radically different from modern ones. If earlier, at the dawn of the Internet, viruses were created to disrupt the computer of the "victim" for no reason, without a special purpose, now the cornerstone is practical. An example of the first generation program is the "Win95 CIH" (worm virus) that appeared in 1996, which at a certain time destroyed data on hard drives or made computers unworkable. Such malicious programs are still being created, but more sophisticated and much less common. For example, now such a "meaningless" virus can load the processor with calculations or overflow memory, making the work of the system impossible. All this class is referred to as "worms". To infect it is enough to start (including the function of the autorun function) a file containing the virus code.

The next type is "zombies". Famous botnets are created with the help of such virus programs. An infected computer that has access to the Internet, by the network command of its creator, starts sending spam messages or attacking the target server (DDos). Since there are many infected computers, they form a whole network (a botnet).

Now viruses-Trojans (backdoors) are very dangerous. With the development of the Internet, many users are more likely to make purchases on the Web, using passwords for bank cards, bills, electronic money, etc., for the payment. A virus of this class that infects a computer monitors the user's actions and sends them a log (including secret passwords) to the virus writer.

In fact, there are many more versions of viruses, and their full review can take up the volume of a small book. From the above it follows that now a comprehensive anti-virus protection system installed on the computer is a must. By the way, you can get infected by visiting even known "clean" sites.