Computer virus
The main fear of any person who uses a computer is that of catching a computer virus which, as with normal biological viruses, can have more or less serious effects. Computer viruses are, in fact, software that silently acts on the computer to do something unauthorized. In antivirus labs, there are researchers who spend their time studying these codes in order to determine how they are programmed, what kind of damage they do, and how they spread.In this guide, we will show you the different types of computer viruses most common and dangerous that can affect a modern computer, also trying to understand how to recognize them in time, so as to be able to avoid them and save the computer from certain formatting.

READ ALSO: How to protect your PC from viruses on the internet

Dangerous PC viruses: which ones to avoid

An antivirus finds and disinfects the virus if it is caught as soon as it is run or on download. In some cases, it may happen that the virus is unintentionally installed on the computer, perhaps accompanied by a scam program and that when it comes into action, it manages to evade the antivirus which thus becomes ineffective. Let’s see together which are the viruses that we absolutely must fear on Windows.

Boot Sector Virus

The term “boot sector” is a generic name for the boot information used by any operating system. In modern computers, this sector is called the “master boot record” and is the first sector on a partitioned hard drive.
A boot sector virus is highly destructive but it has not practically disappeared from circulation; they were popular until some time ago when floppy disks were still used to boot the computer.


This type of virus can spread in various ways but generally spread by downloading deceptive programs. Behind apparently useful programs, during installation or execution, malicious code, called a Trojan, also starts. These are almost always advertising viruses that the internet is full of, which, in the best cases, stand out with the installation of unpleasant toolbars, change the homepage and modify the search provider. In the most serious cases, on the other hand, they steal passwords, create instability and errors, open web pages automatically, spread data externally. The general recommendation is not to download randomly from the internet and also to be careful not to trust sites that can deceive the user.
There are still many free download programs out there that actually contained Trojan viruses or malware. It must also be said that certain types of programs that serve to make multiple computers communicate on the network are also Trojans but they are not viruses because they perform authorized actions of connection to the outside. Trojans do not spread by themselves and are always recognizable in the task manager because they are active programs.


This can be a type of virus that comes into action when executed by the inexperienced (direct) user or automatically when the computer is started. Worms start like normal programs but replicate themselves indefinitely until all memory is saturated. The worm is a virus that does not bind to any other file on your computer and acts independently. Sometimes they exploit the vulnerabilities of other programs to create damage or to allow hackers to enter your PC. Among the famous Worms how to forget Worm Blaster, a real nightmare for those who had Windows XP as an operating system.


Worms and Trojans can increase the level of infection by installing a Keylogger, programs that record the keys on the computer and transmit what is written to the hacker.
This type of threat is very serious as the pirate can steal our passwords for accessing banking and e-commerce sites, as well as obtaining our credit card details.

File infector Virus

Perhaps it is the most common type of virus that takes root in a file by hiding itself. The virus can overwrite the files it infects or in some parts of it so the programs fail and do not go as expected. The only solution is to delete all infected files, which is usually done with normal virus scanning.
They have practically disappeared from circulation, replaced by much more powerful and destructive viruses as well as effective (able to make the hacker earn something in terms of money and blackmail).

Macro Virus

A large variety of programs including Microsoft Excel or Word provide support for macros, automated special actions. Unfortunately, this automation of tasks can also be exploited by a virus, which can thus hide within a seemingly harmless office document.
This virus mainly affects Microsoft Outlook, the e-mail client, which can send e-mails automatically, with a virus attached.

Virus multipartito (Multipartite)

A virus of this type is very dangerous due to its ability to spread. It can perform various actions on an infected computer depending on variables, such as the installed operating system or the existence of certain files.
Fortunately, they are increasingly rare, but in the past, they have made it difficult to use PCs by restricting the formatting of many workstations.

Polymorphic virus

A polymorphic virus is among the most dangerous versions of a computer virus. It has the ability to mutate over time after each execution. This type of virus can affect a computer without giving any sign; after even a month, it begins and evolves and creates more and more frequent problems.

Antivirus may not notice the polymorphic virus if it is in its infancy and remains hidden and inactive. Its behavior can also be assumed by other types of viruses, so as to escape all control systems.

Resident Virus

The Resident Virus enters the memory of a system; once this settlement is completed it is able to perform actions independently and, even by deleting the file responsible for the infection, it remains alive and well. Some of these viruses are rootkit, a term that does not mean viruses but that can identify techniques used by viruses to ensure execution when the computer is restarted or even after a format.
Thankfully, they are increasingly rare, but they posed a major threat to PCs along with polymorphic viruses.

Web Virus Script

Many websites today are web applications, real programs running on your browser. Some sites automatically run malicious scripts which, if not blocked in time, cause even heavy damage. Usually, a warning pop-up, an authorization request, or a message appears (that never happened: your computer is infected, do you want to scan now? OK).
In these cases, it is absolutely necessary to close everything and not to accept anything that comes from a site that you do not know. In another article, I also wrote how to block sites with viruses.


The newest and most widespread viruses currently are undoubtedly Ransomware, the blackmail viruses that block every operation on the PC, also taking personal files hostage (which are encrypted). To be able to access the files and unlock the computer you have to pay the criminals, but often a vicious circle is established: we pay to have no problems and the infection hides (Resident Virus) or worse mutes (polymorphic), making it impossible to completely extinguish it.
Obviously, we avoid paying any blackmail and rely on cleaning and unlocking tools for encrypted files as seen in guide 10 Anti-Ransomware against Ransom or Crypto virus.

Virus Miner

These viruses place themselves in automatic execution and exploit the hardware resources of the PC to mine cryptocurrency on behalf of the hacker, who in fact enriches himself behind us while our programs run slowly (in particular the games that exploit the video card, an indispensable component to undermine). These virus miners are installed on websites or via secure free applications, so you have to be very careful with suspicious processes.
To stop virus miners we can read our guide Block programs that mine Bitcoins on the sly.


These are the main virus-type threats we can fall into with any Windows operating system, including Windows 10 (very secure compared to its predecessors but still vulnerable). In order to stop them, it is advisable to have an updated antivirus (see best free antivirus in Italian) and often scan with other programs, such as those seen in the guide remove malware and viruses from your pc.

To learn more about the guide we can read the article on types of malware bearing in mind that viruses are only one of the categories of cyber threats that you need to protect yourself from.


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