What are computer viruses, their types

Almost every computer owner, if not yet familiar with viruses, must have heard various tales and stories about them. Most of which are, of course, exaggerated by other novice users.


  • So what is a virus?
  • Types of computer viruses
    • The very first viruses (history)
    • Software viruses
    • Macroviruses
    • Script viruses
    • Trojans

So what is a virus?

computer viruses

A virus is a self-replicating program. Many viruses do nothing destructive at all with your PC, some viruses, for example, do a little dirty trick: displays some picture on the screen, launches unnecessary services, opens Internet pages for adults, etc. But there are those that can display your computer is out of order by formatting the drive, or corrupting the motherboard Bios.

To begin with, it is probably worth understanding the most popular myths about viruses walking on the net.

1. Antivirus – protection against all viruses

Unfortunately, it is not. Even with a sophisticated antivirus with the latest database, you are not immune to a virus attack. Nevertheless, you will be more or less protected from known viruses, only new ones unknown to the anti-virus database will pose a threat.

2. Viruses spread with any files

This is not true. For example, with music, video, pictures – viruses do not spread. But it often happens that a virus disguises itself as these files, forcing an inexperienced user to make a mistake and launch a malicious program.

3. If you have contracted a virus – your PC is under serious threat

This is also not the case. Most viruses do nothing at all. It is enough for them that they simply infect programs. But in any case, it is worth paying attention to this: at least, check the entire computer with an antivirus with the latest database. If you got infected with one – then why couldn't the second ?!

4. Do not use mail – a guarantee of safety

I'm afraid it won't help. It happens that by mail you receive letters from unfamiliar addresses. Your best bet is to simply not open them, and immediately delete and empty the trash. Typically, the virus is sent in a letter as an attachment, launching which, your PC will be infected. It will be protected quite easily: do not open letters from strangers … It will also not be superfluous to configure anti-spam filters.

5. If you copied an infected file, you have become infected

In general, until you run the executable file, the virus, like a regular file, will simply lie on your disk and will not do anything bad to you.

Types of computer viruses

The very first viruses (history)

This story began about 60-70 years in some US laboratories. On a computer, in addition to the usual programs, there were also those that worked by themselves, not controlled by anyone. And everything would be fine if they did not overload the computers and do not waste resources in vain.

After a dozen years, by the 80s, there were already several hundred such programs. In 1984, the term “computer virus” itself appeared.

Such viruses usually did not hide their presence from the user. Most often, they interfered with his work by showing some messages.

Brain -virus


In 1985, the first dangerous (and most importantly, rapidly spreading) computer virus, Brain, appeared. Although, it was written with good intentions – to punish pirates who illegally copy programs. The virus only worked on illegal copies of software.

The heirs of the Brain virus survived for about a decade, and then their population began to decline sharply. They did not act cunningly: they simply wrote their body into a program file, thereby increasing in size. Antiviruses quickly learned how to size and find infected files.

Software viruses

Following the viruses that were attached to the body of the program, new types began to appear – in the form of a separate program. But, the main difficulty is how to get the user to launch such a malicious program? It turns out to be very simple! It is enough to call it some kind of breaker for the program and put it on the net. Many people simply download, and despite all the warnings of the antivirus (if any), they will still launch …

In 1998-1999 the world shuddered from the most dangerous virus – Win95.CIH. He was knocking out the Bios of the motherboard. Thousands of computers around the world have been disabled.

virus mail

A virus spread through email attachments.

In 2003, the SoBig virus was able to infect hundreds of thousands of computers by itself attaching itself to messages sent by the user.

The main fight against such viruses: regular OS update Windows, installation of antivirus. Also refuse to launch any programs obtained from dubious sources.


Many users, probably, do not even suspect that in addition to executable files exe or com, ordinary files from Microsoft Word or Excel can also carry a very real threat. How is this possible? It's just that the VBA programming language was built into these editors at one time, so that you could add macros as an addition to documents. Thus, if you replace them with your own macro, a virus may well turn out …

Today, almost all versions of office programs, before launching a document from an unfamiliar source, will certainly ask you if you really want to run macros from this document, and if you click on the 'no' button, then nothing will happen, even if the document was with a virus. The paradox is that most users click the 'yes' button themselves …

One of the most famous macro viruses is Mellis’y, which peaked in 1999. The virus infected documents and via Outlook mail sent an email with infected content to your friends. Thus, in a short time, tens of thousands of computers around the world were infected with it!

Script viruses

Macroviruses, as a specific species, are included in the group of scripting viruses. The bottom line is that not only Microsoft Office uses scripts in its products, but other software packages also contain them. For example, Media Player, Internet Explorer.

Most of these viruses are spread by means of attachments to letters, via e-mail. Often attachments are disguised as some newfangled picture or musical composition. In any case, do not launch or even better do not open attachments from unfamiliar addresses.

Often, users are misled by the file extension … After all, it has long been known that pictures are safe, then why can't you open a picture sent by mail … By default, Explorer does not show file extensions. And if you see the name of the picture, like 'interesnoe.jpg' – this does not mean that the file has exactly that extension.

In order to see extensions, enable the following option.

Local Disk (C) _2013-11-16_20-25-39

Let's show with an example Windows 7. If you go to any folder and click 'organize / folder and search options' you can get to the 'view' menu. This is where our cherished checkmark is.

Folder options_2013-11-16_20-25-54

Uncheck the option 'hide extensions for registered file types', and also enable the 'show hidden files and folders' function.

Folder options_2013-11-16_20-25-59

Now, if you look at the picture sent to you, it may well turn out that 'interesnoe.jpg' suddenly became 'interesnoe.jpg.vbs'. This is the whole trick. Many novice users have fallen into this trap more than once, and they will come across more …

The main protection against script viruses is the timely updating of the OS and antivirus. Also, refusal to view suspicious letters, especially those that contain incomprehensible files … By the way, it will not be superfluous to regularly backup important data. Then you will be 99.99% protected from any threats.


Although this species has been classified as a virus, it is not directly one. Their penetration into your PC is in many ways similar to viruses, only their tasks are different. If a virus has the task of infecting as many computers as possible and performing an action to remove, open windows, etc., then the Trojan program, as a rule, has one purpose – to copy your passwords from various services, to find out some information. It often happens that a Trojan horse can be controlled over a network, and upon the order of the owner, it can instantly restart your PC, or, even worse, delete some files.

It is also worth noting one more feature. If viruses often infect other executable files, the Trojans do not do this, it is a self-contained standalone program that works by itself. It often disguises itself as some kind of system process so that it is difficult for a novice user to catch it.

In order not to become a victim of Trojans, firstly, do not download any files, such as hacking the Internet, hacking some programs, etc. Secondly, in addition to antivirus, you also need a special program, for example: The Cleaner, Trojan Remover, AntiViral Toolkit Pro, etc. Thirdly, it will not be superfluous to install a firewall (a program that controls Internet access of other applications), with manual configuration, where all suspicious and unknown processes will be blocked by you. If the Trojan horse does not get access to the network, half the work has already been done, at least your passwords will not disappear anywhere …

Summing up, I would like to say that all the measures and recommendations taken will be useless if the user himself, out of curiosity, launches files, disables antivirus programs, etc. The paradox is that virus infection occurs in 90% of cases through the fault of the PC owner. Well, in order not to become a victim of those 10%, it is enough to sometimes back up files. Then you can be almost 100% sure that everything will be OK!

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