The main fear of any person who uses a computer is to catch a computer virus which, like normal biological viruses, can have more or less serious effects. Computer viruses are, in fact, software that acts silently on the computer to do something unauthorized. In antivirus laboratories there are researchers who spend their time studying these codes in order to determine how they are programmed, what type of damage they do and how they spread. Personally, I find this field interesting and I like, every now and then, to read about the different types of viruses that exist, even if we often don't understand each other. So let's see the different types of viruses that are most common and dangerous that can affect a computer, also trying to understand how they can be recognized.
READ ALSO: How to protect your PC from viruses on the internet
The problem is that an antivirus finds and disinfects the virus if it is caught on entry. In some cases it may happen that the virus is unintentionally installed on the computer, perhaps accompanied by a scam program, and, when it enters into action, it manages to evade the antivirus which becomes so ineffective. In general, the most common and dangerous types of viruses are :
1) Boot Sector Virus
The term "boot sector" is a generic name that indicates the boot information used by any operating system. On modern computers this sector is called the "master boot record" and is the first sector on a partitioned hard disk. The Boot sector virus is destructive but it practically no longer exists; it was popular until quite some time ago, when floppy disks were still used to boot the computer.
2) Trojan
This type of virus can spread in various ways but, above all, with the download of deceptive programs. Behind seemingly useful programs, during installation or execution, a malicious code, called Trojan, also starts. These are almost always advertising viruses with which the Internet is full, which, in the best cases, are noticed with the installation of unpleasant toolbar, change the homepage and modify the search provider. In more serious cases, on the other hand, they steal passwords, create instability and errors, open web pages automatically, disseminate 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.
I have seen many Italian blogs, for example, advertise programs (obviously earning over them) to download for free which, in reality, contained Trojan viruses or malware. It must also be said that certain types of programs that are used to make more computers communicate on the network, are also Trojans but 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.
3) Direct Virus and Worm
This can be a type of virus that comes into action when it is executed by the inexperienced (direct) user or automatically when the computer starts. Direct-acting viruses hardly exist anymore while Worms, those that start as normal programs when the computer starts, are very common. The worm is a virus that does not bind to any other computer file and that acts independently. Sometimes they exploit the vulnerabilities of other programs to create damage or to allow hackers to enter their PC. I can't forget the hell caused so many years ago by the famous Worm Blaster that still affects all computers that run Windows XP without service pack 2.
Worms and Trojans can bring Keyloggers, programs that record keys on the computer and transmit what is written to a stranger.
4) File infector Virus
Perhaps it is the most common type of virus, strictly speaking, that takes root in a file by hiding itself. The virus can overwrite the files it infects or in some of its parts so the programs go wrong and do not do what was expected. The only solution becomes to delete all infected files, which is typically done with normal antivirus scanning.
5) Macro Virus
A large variety of programs, including Microsoft Excel or Word, provide support for macros, special automated actions. Unfortunately, this makes it possible for a virus to hide inside an apparently good document. This virus mainly affects Microsoft Outlook, the email client, which can send mail automatically, with virus attached.
6) Multiparty virus
A virus of this type is very dangerous for its spreading ability. It can perform various actions on an infected computer depending on variables, such as the installed operating system or the existence of certain files.
7) Polymorphic viruses
The polymorphic virus is the most common and most dangerous type of infection.
It has the ability to change over time after each execution.
This type of virus can hit a computer without giving any sign; then, after even a month, it begins and evolves and creates more and more frequent problems.
An antivirus may not notice the polymorphic virus if it is in the embryonic stage and remains hidden and inactive.
8) The Resident Virus is the one that is inserted into the memory of a system. At that moment it is able to perform actions independently and, even by deleting the file responsible for the infection, it remains alive. Some of these viruses are rootkits, which in itself does not mean viruses. However, it happens that, even if you delete every infected file, when you restart your computer, it recurs.
The most popular antiviruses also have antirootkit functions, but the best way to recognize rootkit viruses is manually with Hijackthis.
9) Web Virus Script
As seen, many websites today are web applications, real programs run on their browser. Viewing online videos, for example, requires running a specific code that loads the player. Some sites automatically launch malicious scripts which, if they are not blocked in time, also cause heavy damage. Usually a warning pop up appears, an authorization request or a message (that has never happened: your computer is infected, you want to scan now "> block sites with viruses.
To continue the guide, you can read the article on the types of malware keeping in mind that viruses are only one of the categories of cyber threats that you need to protect yourself from.
Having an updated antivirus (see best free antivirus in Italian) is essential but you should not think that the antivirus alone is infallible and 100% protects the Windows PC.
Occasionally, especially if stability problems are encountered, if the PC shuts down on its own or if some programs do not work, a manual check must be done.
As written in the guide to remove malware and viruses from your PC, you need to have programs like Malware Bytes, SuperAntispyware Portable and NoVirusThanks portable. A portable program, which requires no installation, is usually not fooled by viruses.
With the Task Manager powered by Process Explorer you can recognize the active processes on the computer that have not been verified and that, potentially, can be viruses.
