What are computer virus, its types and signs

The topic of today’s article is computer viruses. Types of computer viruses, principles of their work, ways of infection with computer viruses.

What are computer viruses?

Computer virus: This is a specially written program or assembly of algorithms that are written with the aim of joking, harming someone’s computer, gaining access to your computer, to intercept passwords or extort money. Viruses can self-copy and infect your programs and files, as well as boot sectors, with malicious code.

Types of malware.

Malicious programs can be divided into two main types.

  • Viruses
  • Worms.


Viruses spread through a malicious file that you could download on the Internet, or it may appear on a pirated disk, or often transfer them via Skype under the guise of useful programs. (I noticed that schoolchildren often come across the latter, they are supposedly given a mod for a game or cheats it may actually be a virus that can harm).

The virus enters one of its programs code or disguises itself as a separate program in the place where users usually do not go (folders with the operating system, hidden system folders).

The virus cannot start by itself until you launch the infected program yourself.


Worms already infect many files on your computer, for example, all exe files, system files, boot sectors, etc. Worms most often penetrate the system themselves, using vulnerabilities in your OS, your browser, and a specific program.
They can penetrate through chats, communication programs such as skype, icq, can be distributed via e-mail.

They can also be on sites, and using the vulnerability of your browser to penetrate your system.

Worms can spread over the local network, if one of the computers on the network is infected, it can spread to other computers, infecting all files in its path.

Worms try to write to the most popular programs. For example, now the most popular browser is “Chrome,” so scammers will try to write for it, and make malicious code on sites for it. Because it is often more interesting to infect thousands of users who use a popular program than hundreds with an unpopular program.

Although chrome constantly improves its security and protection.

The best protection against network worms is to update your programs and your operating system. Many people neglect updates, which they often regret.

A few years ago, I noticed the next worm.

But It obviously didn’t get through the Internet, but most likely through a pirated disk. The essence of his work was such – he created a copy of each folder on a computer or on a USB flash drive. But in fact, he did not create a similar folder but an exe file. When you click on such an exe file, it spreads even more throughout the system. And then you just got rid of him, come to a friend with a flash drive, throw off his music and return with a flash drive infected with such a worm and again you had to remove it. Whether this virus caused any other harm to the system, I do not know, but soon this virus ceased to exist.

The main varieties of viruses.

In fact, there are many types and varieties of computer threats. And everything is simply impossible to consider. Therefore, we will consider the most common in recent years and the most unpleasant.

Viruses are:

  • File – located in an infected file, activated when the user turns on this program, they themselves cannot be activated.
  • Bootable – can be booted when windows are booted upon startup, when inserting a flash drive or the like.
  • Macro viruses – these are various scripts that can be located on the site, can send them to you by mail or in Word and Excel documents, perform certain functions stored in the computer. They can use vulnerabilities of your programs.

Types of viruses.

  • Trojans
  • Spies
  • Extortionists
  • Vandals
  • Rootkits
  • Botnet
  • Keyloggers

These are the most common types of threats that you may encounter. But in fact, there are many more.

Some viruses can even be combined and contain several types of these threats at once.

Trojan programs

The name comes from the Trojan horse. Penetrates into your computer under the guise of harmless programs, then it can open access to your computer or send your passwords to the owner.
Recently, such Trojans called stealers are common.

They can steal saved passwords in your browser, in email game clients. Immediately after launch, it copies your passwords and sends your passwords to email or hosting to an attacker. It remains for him to collect your data, then they are either sold or used for their own purposes.

Spies (spyware)

They track user actions. What sites does he visit or what does the user do on his computer.


These include Winlockers. The program completely or completely blocks access to the computer and requires money for unlocking. For example, put on an account or so on. In no case, if you get into this, you should not send money. Your computer will not unlock, and you will lose money.

You have a direct route to the Drweb website, where you can find how to unlock many winlockers by entering a specific code or performing certain actions. Some winlockers may disappear for example in a day.


Vandals can block access to antivirus sites and access to antiviruses and many other programs.

Rootkits (rootkit)

Many viruses are hybrids. They may contain various viruses. They can get access to your PC, and a person will have full access to your computer, and they can merge to the kernel level of your OS. Came from the world of Unix systems, They can mask various viruses, collect data about the computer and about all processes of the computer.


Botnet is a pretty nasty thing. Botnets are huge networks of infected “zombie” computers that can be used for DDoS sites and other cyber attacks using infected computers. This species is very common and difficult to detect, even antivirus companies may not be aware of their existence for a long time. Many can be infected by them and not even suspect about it. You are no exception, and maybe even I.


They intercept everything that you enter from the keyboard (sites, passwords) and send them to the owner.

The main ways of infection

  • Vulnerability of the operating system.
  • Vulnerability in the browser
  • The quality of the antivirus is lame
  • Stupid user
  • Removable media.

OS vulnerability

No matter how hard they try to rivet the protection for the OS, there are security holes over time. Most viruses are written under windows since it is the most popular operating system. The best protection is to constantly update your operating system and try to use a newer version.


This is due to browser vulnerabilities, especially if they are again old. It is treated as a frequent update. There may also be problems if you download browser plug-ins from third-party resources.


Free antiviruses that have less functionality as opposed to paid ones. Although paid ones do not give 100 results in defense and they misfire. But it is desirable to still have at least a free antivirus. I already wrote about free antiviruses in this article.

Stupid user

Clicks on banners, click on suspicious links from letters, etc., install software from suspicious places.

Removable media

Viruses can be installed automatically from infected and specially prepared flash drives and other removable media. Not so long ago, the world heard about the vulnerability of BadUSB.

Types of infected objects

Given below are some types of objects which can make your system infected.


Infects your programs, system and regular files. Boot sectors are resident viruses. The boot sectors of the computer are infected, as the name implies, ascribe their code to the startup of the computer and are launched when the operating system starts. Sometimes they mask well, which is difficult to remove from startup.


Documents word, excel and the like. Using macros and vulnerabilities, Microsoft office contributes its malicious code to your operating system.

Signs of computer virus infection

Not the fact that with the appearance of some of these signs means the presence of a virus in the system. But if they are available, it is recommended to check your computer with antivirus or consult a specialist.

Computer Overload

One common symptom is a heavy computer overload . When your computer is slowly running, although nothing seems to be turned on, programs that can heavily load the computer. But if you have an antivirus, notice the antiviruses themselves load the computer very well. And if there is no such software that can load, then viruses are more likely here. In general, I advise you to reduce, for starters, the number of running programs in autorun.

Slow loading of programs

Slow loading of programs can also be one of the signs of infection. But not all viruses can heavily load the system; some are almost difficult to notice changes.

System errors Drivers cease to work, some programs start to work incorrectly or often crash with an error, but let’s say this was not noticed before. Or, programs often restart. Of course, this happens because of antiviruses, for example, the antivirus deleted by mistake, considering the system file to be malicious, or deleted the really infected file, but it was associated with the system files of the program and the removal caused such errors.

Unwanted ad pop-ups and cd drive ejection

  • The appearance of advertising in browsers or even on the desktop banners begin to appear.
  • The appearance of non-standard sounds during computer operation (squeak, clicks for no reason and the like).
  • A CD / DVD drive opens by itself , or simply starts to read a disc, although there is no disc. Long turn on or off the computer.

Hijacking your passwords

If you notice that various spam is being sent on your behalf from your inbox or social network page, as the probability that a virus entered your computer and passed passwords to the owner, if you notice this, I recommend that you check it with an antivirus without fail (although it’s not a fact that it’s exactly the attacker received your password).

Hard drive access

Frequent hard drive access. Each computer has an indicator that blinks when using various programs or when copying, downloading, moving files. For example, your computer is just turned on but you are not using any programs, but the indicator starts flashing often, allegedly using programs. These are already viruses at the hard drive level.

That’s actually considered computer viruses that you may meet on the Internet. But in fact, there are many more of them, and it is not possible to fully protect yourself, unless you use the Internet, buy disks, or even turn off the computer.

If possible, I advise you not to neglect the use of virtual machines or the sandbox .

Take care of yourself and your computers.

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