Computer viruses are small software programs designed to spread from one computer to another, interfering with computer operation. They can do various things, from corrupting and deleting your computer’s information to using your email program to spread to other computers. They are even able to erase everything on your hard disk.

Nearly all viruses are spread through online downloads, hiding in illegal applications, files, or programs that you download to your computer. They may also be found in email attachments and sometimes through messenger programs, which is why it’s vital that you never open any attachments unless you know who it is from and you are expecting it. They may be as benign as a humorous picture or even hide in sound and video files.

There is a huge selection of viruses and malicious software that may attack your computer. Continue reading to find out more about the various kinds and ways to protect yourself from them.

Most Frequent Viruses and Malicious Programs

Resident Viruses

This is a form of virus which resides on your RAM; out of there, it may overcome and disrupt all options accomplished by your system, corrupting files and applications that are closed, opened, renamed, copied, etc. Examples include:

    • Randex
    • CMJ
    • Meve
    • MrKlunky
Multipartite Viruses

These viruses have been distributed through infected media and usually hide in your computer’s memory, slowly moving into the boot sector of the hard disk and infecting your executable files. Its objective is to infect all .exe files through your computer system.

Direct Action Viruses

The major aim of these viruses is to replicate, then do it when implemented. When a particular condition is met, they move into action and infect files in the folder or directory they’re in, in addition to in directories that are specified in the AUTOEXEC.BAT file PATH. This batch file is always located in the main directory of your hard disk and carries out specific operations once your computer is booted.

Overwrite Viruses

These viruses delete the information contained in the documents they infect, making them totally useless. The only way to “clean” a document that has been infected by an overwrite virus would be to delete it entirely, which will let you eliminate the original content. Examples include:

    • Trj.Reboot
    • Way
Boot Viruses

These viruses have an effect on the boot sector of your hard disk, where the information and applications are saved that make it feasible to start your own computer. Examples include:

    • AntiEXE
    • Polyboot.B
Macro Viruses

Macro viruses infect documents that are created using specific programs or applications that contain macros — mini-programs making it feasible to automate a set of operations so that they are performed as one act, saving the user from having to carry them out separately. Examples include:

    • Relax
    • Bablas
    • Melissa.A
Directory Viruses

These viruses alter the paths indicating the location of a document. When you execute a program (a file with the extension .EXE or .COM) that has been infected by this virus, then you are unknowingly running the app; the original document or program was relocated. Once your system is infected, it becomes incredibly difficult — if not impossible — to find your original files.

Polymorphic Virus

These viruses intercept or detach themselves otherwise — using different algorithms and encryption keys — each time they infect a system, which makes it impossible for antivirus programs to locate them using string or trademark searches. Additionally, it allows them to create a significant number of copies of these. Examples include:

    • Satan Bug
    • Marburg
    • Tuareg
File Infectors

These viruses infect applications or executable files (files with an .EXE or .COM expansion). When one of these programs is run, either directly or indirectly, the virus is activated and generates the damaging effects it is programmed to perform. The vast majority of current viruses belong to the category and can be categorized depending on what they do.

Encrypted Viruses

These viruses contain encrypted malicious code and typically replicate by decrypting spreading and themselves. When encrypted, it is difficult for antivirus software to detect them. However, as soon as they decrypt themselves in an effort to disperse, your antivirus can capture them fairly easily.

Companion Viruses

These could be considered file infector viruses, like a resident and direct action viruses. Once they get into your system, they follow other documents that already exist; Quite simply, so as to perform their own disease routines, they could either wait until a program is run (resident viruses) or act instantly by making copies of themselves (direct action viruses). Examples include:

    • Stator
    • Asimov.1539
    • Terrax.1069
Network Viruses

These viruses quickly spread through a native Network Area (LAN), and sometimes throughout the internet. They generally multiply through shared resources like folders and drives; when they infect a computer, they hunt through the system to find new prey. Once they have completed infecting that computer, they proceed to another, repeating the cycle. The most dangerous network viruses are:

    • Nimda
    • SQLSlammer
Nonresident Viruses

These viruses are like resident viruses (though they do not host themselves on your computer’s RAM), and include a finder module and a replication module. The finder module finds new files to infect; when it finds a new executable file, it calls the replication module to infect it.

Stealth Viruses

These viruses attempt to “trick” your antivirus software by intercepting its requests to the operating system. They could successfully hide from some antivirus apps, but not all.

Sparse Infectors

These viruses try to prevent detection by using different methods, like just infecting a document every 10th time it’s implemented or files whose names start with certain letters of the alphabet. They’re more difficult for antivirus programs to find, but as software gets more advanced they are easier to discover.

Spacefiller (Cavity) Viruses

These viruses try to be smart by housing them indoors vacant spots in a program file’s code without damaging the app. Since the virus does not increase the duration of the program’s code, it is more difficult to detect. The Lehigh virus was an early instance.

FAT Viruses

The File Allocation Table, or FAT, is the section of your hard disk used to connect information and is crucial to maintain your computer working normally. This virus can be particularly dangerous, as it may prevent access to segments of the driveway where important files are saved, and any damage it causes can lead to information loss from the individual files and entire directories.


Technically, worms are not viruses; they are very much like viruses, however, they also have the capability to self-replicate and may result in negative effects on your system. Most of all, however, is they are treated exactly the same as viruses from your antivirus software and maybe discovered and removed. Some examples of worms include:

    • Lovgate.F
    • Sobig.D
    • Mapson
Trojans (Trojan Horses)

These are not viruses but are a sort of malicious code that could infect your computer. Unlike viruses, they do not replicate by infecting other files. But like viruses, they may be detected by your antivirus software.

Logic Bombs

These are camouflaged sections of different applications whose aim is to destroy data on your computer once certain requirements are met. Since they do nothing until launched, they frequently go unnoticed, and the results of the assault can be incredibly destructive.

Preventing infection by viruses and other malicious applications.

Because many malicious programs, like “worms,” traveling the internet searching for vulnerable computers, you can be at risk of infection by simply being online. Fortunately, though new viruses are being created constantly, there are steps you can take to safeguard your computer.

Your main defense is antivirus software; installing and upgrading this program will help protect your computer. Regrettably, while antivirus software is a vital element of your defense, it is not sufficient to keep you fully protected. You should also be sure that you’re upgrading your operating system frequently. Windows users can install critical updates through Windows Update, while Macintosh users may click on their Apple menu and select Software Update.

Other virus prevention tips
    • Do not open emails with attachments when the message is suspicious — even if they are from a friend or acquaintance.
    • Do not download files from strangers, and be careful when downloading files from the internet.