Present day viruses

There are a huge number of computer viruses in the world. To establish their exact number (along with all modifications and upgrades) no one is taken. Instead, it is customary to calculate the loss or intensity of a virus attack. But, neither one nor the other allows users to understand what, exactly, how and why it gets to their computer?

Reasons for creating viruses
There are no reasons for the appearance of viruses as such. These are the reasons for human stupidity. We simply have the actual value – a huge number of computer viruses and virus programs that inhabit the Internet along with sites. It’s true that it’s worth highlighting several reasons, it’s still worth it, they are especially clear to any person.
Childishness
Banal reason. Someone wanted to try “what happens if?” True, almost no one is now engaged in viral childishness. However, it is impossible not to mention it. Indeed, this is how the first virus arose. It was created to show people “I can do this, but you can’t do anything.” However, as happens in horror films, our experimental virus escaped from control and began to multiply and multiply. Fortunately, then the network was isolated and decided that such things should not be played. So, in fact, viruses were recognized as dangerous. As they say in the famous phrase “A small chest just opened.” What one managed to do, the others managed to repeat.
Way to make money
The most controversial reason. There are viruses that are designed to steal passwords. Others sleep until the right moment, and then attack a particular site. Still others are slowly starting to send your personal data somewhere on the Internet. Fourth block the system or sites, requiring a key. Since this bunch of viruses will not be of different sizes, they pursue one goal – the enrichment of the creator. Blackmail, trivial swindle, obtaining keys and passwords. All this leads to theft of money in different sizes. And what is the connection to the bank’s network worth when it was “inundated” with requests from hundreds of thousands of computers around the world. The latter, however, occurred once or twice. But the film directors really like to beat such subjects.
Revenge
Perhaps this is the most unusual reason. So, once a guy made his ex-girlfriend a Trojan program, which on the day they met (every month) destroyed her OS, and she settled in no where. Actually, the girl was not very smart, and her friends were no better. So this OS killer has spread. Fortunately, a cure for it was found very quickly, the algorithm was too primitive. However, the case has remained in world practice and one should not forget about such a reason as revenge (a girl, colleagues, former bosses, parents, a school teacher, no matter who).
Other
You will not be surprised to learn that sometimes quite interesting hypotheses are put forward. And that viruses are written by the developers of antivirus software, no matter what is left without work. And that viruses are written under the order of the government with the aim of some kind of control of the population. We will not discount these reasons. But personally, to the author, they sometimes seem comical.
Virus classification
No matter what the objectives of the attacker who creates the virus, they will remain with him. Neither the program code nor the distribution method will indicate this to us (although the code may indicate it, especially if this is the second reason). However, they can indicate to us the type of virus, and therefore suggest what to expect from it. According to the algorithm of work (the behavior of a computer virus when a computer is infected), it is customary to classify viruses as follows.
Parasitic viruses
They settle on a computer and begin to multiply, rewriting program code or appending their body to it. In general, they are not dangerous until a certain point. They can be compared with parasitic worms, as long as there are few of them, they almost do no harm to the host organism, but the more they are, the more noticeable their presence. They begin to noticeably load the memory and processor, resulting in a drop in system performance. Fortunately, such viruses are calculated quite easily, and treating them almost does not cause inconvenience (in the most advanced cases, you have to reinstall the system, almost without losing valuable data).
Mutant viruses
The most difficult to detect viruses. They do not appear in the same form twice, but are distributed over the networks in an encrypted form, preserving the original structure. On the infected machine, they are decrypted and begin their subversive activities. You can detect them only at the time when they begin to act. Any type of virus can appear as a mutant; it is enough to organize an encryption algorithm in it. At the moment, these viruses are not as much a threat as at the dawn of their existence, since antivirus programs have become more flexible and predict the possibility of their appearance.
Trojan programs
These viruses do not spread as fast as worms, cannot modify themselves, and are sometimes easy to detect.