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What is a Computer Virus?

A computer virus, like the influenza virus, is designed to travel from host to host and duplicate itself. In the same way, as flu viruses cannot reproduce and spread without a host cell, computer viruses cannot proliferate and propagate without programmings, such as a file or document.

A computer virus is a harmful application that copies itself onto another program to propagate itself. In other words, the computer virus multiplies by infecting other executable code or documents. The goal of a computer virus is to infect vulnerable computers, acquire administrative access, and steal sensitive data from users. Hackers create computer viruses with malicious intent and exploit deceit to prey on internet users.

What are the Different Types of Computer Viruses?

A computer virus is a kind of malware that inserts its virus code into programs and applications to replicate itself. Malicious code is replicated on the computer, infecting it. Computer viruses exist in a variety of shapes and sizes, and they infect the system in a variety of methods. Here are a few of the most frequent types of computer viruses.

What are the Different Types of Computer Viruses

Figure 1. What are the Different Types of Computer Viruses?

1. Web Scripting Virus

Web Scripting Virus is a kind of virus that can compromise the security of web browsers. When it breaks the web browser's security, it injects malicious code that allows it to take control of the browser and change its settings. This malware spreads in the same way that any other computer infection does.

2. Resident Virus

A resident virus is a type of computer virus that conceals and keeps itself within the computer's memory, allowing it, depending on the virus' programming, to infect any file that the machine runs. A resident virus stores its replication module into memory rather than executing it in order to infect additional files; instead, it activates whenever the operating system loads or performs a certain function. This virus is potentially one of the worst since it may infect the entire system, even attaching itself to anti-virus software, allowing it to infect each file checked by the program.

3. Polymorphic Virus

Polymorphic viruses are sophisticated file infectors that may build changed copies of themselves to avoid detection while maintaining the same fundamental behaviors after each infection. Polymorphic viruses encrypt their codes and employ various encryption keys each time to alter their physical file makeup throughout each infection.

Mutation engines are used by polymorphic viruses to change their decryption routines every time they infect a system. Because typical security solutions do not employ a static, unchanging code, traditional security solutions may miss them. They are considerably more difficult to detect because they utilize complicated mutation engines that create billions of decryption routines.

Polymorphic viruses are typically spread by spam, malicious websites, or other malware. Some of the most well-known polymorphic viruses include URSNIF, VIRLOCK, VOBFUS, and BAGLE or UPolyX.

4. Multipartite Virus

A multipartite virus is a fast-moving virus that attacks the boot sector and executable files concurrently using file infectors or boot infectors. The majority of viruses damage the boot sector, the operating system, or the application files. The multipartite virus has the ability to attack both the boot sector and program files at the same time, causing greater harm than any other virus. Because it hooks on to the hard drive that stores the data needed to start the computer when the boot sector is infected, merely turning on the computer will activate a boot sector virus. Destructive payloads are launched across the program files after the virus has been activated.

5. Macro Virus

In terms of cybersecurity, a macro virus is a virus written in macro, a programming language integrated into software products like Microsoft Office. This programming language is useful because it allows users to automate operations and improve productivity by reducing them to a few keystrokes. Unfortunately, the macro virus has infected the language as well.

A macro virus, like any other virus, works by inserting its code into macros attached to common data files used in office work, such as Microsoft Word, Excel, or PowerPoint files. It's also capable of infecting ActiveX controls and COM add-ins. Once a macro virus has become part of a macro's automatic procedure, all it takes is for you to activate the files or allow the macro to run.

6. File Infector Virus

File infectors Viruses that infect files transfer their code to executable programs such as .COM and .EXE files. The majority of file infectors merely reproduce and propagate, however, some do so accidentally and cause harm to host applications. File infectors can also overwrite host files. Some file infectors have payloads that range from very damaging to innocuous, such as message displays.

7. Boot Sector Virus

A boot sector virus is a type of malware that infects the computer's storage sector, which contains startup data. All of the files necessary to launch the operating system (OS) and other bootable programs are found in the boot sector. The infections run during bootup, allowing them to execute harmful code before numerous protection layers, including antivirus software, are loaded.

Boot sector viruses are divided into two categories. The older types start from the first sector of the storage medium when the machine is turned on. This was especially frequent when floppy disks were used for DOS booting. This earlier infection might conceivably live on other media including CDs, DVD ROMs, flash drives, and other external storage devices. Viruses that infect the master boot record are more prevalent and recent (MBR). Despite the fact that they do not infect the boot sector, these viruses insert themselves into the boot process in the same way that those that do hide destructive operations. True boot sector infections require media to be placed in the machine at boot time, however MBR-infecting viruses do not.

How Does a Computer Virus Attack?

Once a virus has got entry into a recently infected system, it begins to carry out the exploit that the infection's creator intended. Depending on the techniques the virus uses and the privileges of the user who created the infection, the virus may be able to take any action it desires on the target system. A virus might look for Social Security numbers, credit card numbers, and passwords on the local hard drive (HD), then send them back to the attacker. To prevent detection, a virus could remove data or make unwanted changes to the operating system. Virus attacks may also attempt to deny legitimate users access to the system or the data it holds.

Viruses are software programs that are meant to harm your computer by deleting files, corrupting applications, or reformatting the hard drive. Others just copy themselves or flood a network with traffic, rendering all internet activity impossible. Even less harmful computer viruses can cause problems on your system's function, robbing it of memory and inflicting numerous malfunctions.

How Does a Computer Get a Virus?

A virus can infect a computer in many ways, the most common of which involves downloading infected files - either knowingly or unknowingly. Pirated music or movies, photographs, free games, and toolbars, as well as phishing/spammy emails with attachments, are all prominent offenders. Viruses can also be downloaded by going to malicious websites or clicking on links or advertisements that lead to an unknown/unsecured website. Even connecting to a maliciously infected external drive (such as a USB) can infect your computer.

How do Computer Viruses Spread?

When a user accepts an email link, opens an executable file, views an infected website, or opens a malicious online advertisement, a virus is spread. Infected external storage devices, like USB drives, can potentially transfer it. A virus can infect other system software or resources, modify or disable fundamental functionality or applications, and copy, destroy, or encrypt data after infecting the host.

What are the Signs of a Computer Virus?

While some viruses are simply for "enjoyment," the majority of them are designed to steal your usernames and passwords, turn your computer into a botnet, and transmit spam emails via your network.

To list Common Computer Virus Symptoms:

  • Unexpected pop-up windows are a common symptom of a virus infection, particularly if they have nothing that you're working on.
  • ?f the computer is running slower than usual, it can be a sign of a virus.
  • It could be a virus running in the background if you observe your computer accessing the hard disk or SSD when you aren't working on anything.
  • If you find that your computer is running out of storage and you haven't saved anything to take up space, a virus may be the cause.
  • Another clue could be if files start to disappear out of nowhere and you're certain you haven't erased anything by accident.
  • Viruses can cause your computer to crash frequently or display unexpected error messages.
  • If your internet usage seems unusually high, it could be a warning sign of the virus.
  • One of the most common types of viruses is sending spam over your network.
  • Unusual Web Browser Problems can be a sign of a virus.

These are all key indicators of a computer virus infection.

How Do I Prevent Computer Viruses?

You may prevent computer viruses by following the next tips outlined below:

  • Viruses are a serious cyberthreat, that's why it's a good idea to maintain your computers virus-free. As you bank, buy, and surf the web, the software can help protect you against online risks. Therefore Installing and running antivirus software on your devices is necessary if you want to avoid receiving a virus from the internet.
  • Spamming emails are a common way for cybercriminals to transmit viruses. If you cant identify the sender of an email attachment, or if the email appears to be a phishing tactic, the best action may be to ignore it. If you trust the source, open attachments or download files from your email.
  • Cyber attackers might take advantage of security flaws to induce a virus download on devices. When a patch is available, update your software regularly or set your machine to automatically accept updates.
  • Avoid clicking on links to websites with strange names, such as letters and symbols that don't look like words. Websites that are a cyber threat will employ a variety of methods to infect your computer, including drive-by downloads, hosting harmful adverts, and tricking you into clicking on deceptive links.
  • It may seem appealing to obtain a free copy of a game, movie, or application that everyone else must pay for. But you are the product if you do not pay for it. If you download a pirated or illicit version of software, it's potential that your computer or mobile device is in threat.
  • Finally, backing up your devices can help you avoid some of the harm and stress of getting a virus. Also, using a malware scanner ensures that viruses don't get an opportunity to spread further on your network and minimize damage. These programs are simple, inexpensive, or even free.

How to Remove Computer Viruses

Viruses on computers are nearly always undetectable. You could not even realize you have a virus if you don't have anti-virus protection. This is why anti-virus software should be installed on all of your devices.

  • Install a virus scanner or a whole internet security system.
  • Disconnect from the internet while eliminating a virus from your computer to prevent the virus from spreading.
  • Restart your computer in 'Safe Mode' to protect it while you clean the virus.
  • 'Disk Cleanup' might be handy for deleting temporary files. Some viruses are programmed to begin as soon as your computer is turned on.
  • Use your antivirus or internet security program to start a virus scan.
  • If a virus is discovered, it may damage several files. To delete the file(s) and get rid of the virus, choose 'Delete' or 'Quarantine.' Then re-scan your machine to make sure there are no new dangers. Quarantine or destroy the files if dangers are discovered again.
  • Your computer can now be restarted. Simply turn it on like you normally would.
  • If you have reason to believe your credentials have been taken by malware, make sure you update them all to protect your computer from further attacks.
  • Updating your software, browser, and operating system reduces the danger of hackers using holes in older code to infect your machine with malware.

What Are Examples of Computer Viruses?

There are millions of computer viruses on the internet, but only a few have obtained popular and infected lots of PCs. The following are some instances of common computer viruses:

  • Morris Worm
  • Nimda
  • SQL Slammer
  • Stuxnet
  • CryptoLocker
  • Conficker
  • Tinba
  • Welchia
  • Shlayer

What is the Difference Between Viruses and Malware?

Malware is a broad term that refers to any malicious program designed to infect and harm the host system or its users. Any harmful computer program on a computer or mobile device is now referred to as malware. Malware includes computer viruses, worms, Trojan horses, ransomware, rootkit, spyware, and other malicious programs. These programs are installed without the users' permission and can have a variety of negative consequences.

Computer viruses are a subcategory of malware that spreads by "infecting" other files on a hard drive or computer.

Malware can affect any device, but you'll be at varying levels of risk based on what you use. The most common target is Windows PCs. Despite their stronger protections, smartphones and tablets can even be affected by malware. Regardless of the type of infection, there are some common symptoms. If your device suddenly becomes unusually slow, a poorly-written piece of malware is likely using its resources.

Because so many varieties of malware have similar symptoms, it might be difficult to figure out which one is on your device until it tells you, as ransomware does. Whatever type of malware you have, you must act quickly to remove it from your computer and prevent it from spreading to other computers on your network.

Is Worm a Virus?

A computer worm is a type of malware that replicates and spreads through network connections. The computer worm usually infects another machine on the network rather than infecting computer files. The worm does this by cloning itself. The worm's clone inherits this ability, allowing it to infect additional systems in the same way. Computer worms are self-replicating programs that run in the background, unlike viruses that require a host file to infect.

Computer worms take advantage of network flaws. The worm is hunting for an undetected back door into the network. Hackers frequently send phishing emails or instant messages with malicious attachments to get computer worms into circulation for the first time.

Viruses are frequently found in files that are shared or downloaded. When a computer's host file is downloaded, the virus remains asleep until the infected file is activated. Only then will the virus be able to run malicious code and spread to other files on the computer.

When a computer worm enters a system, it copies itself and spreads throughout the network or across an Internet connection. All PCs and servers that connect to the infected device over the network are infected by these copies. Computer worms can easily and swiftly propagate across networks because each consecutive copy of the worm continues the self-replication, execution, and spreading process. The following are the most common signs of a computer worm; the existence of more than one of these symptoms, or the recurrence of these symptoms regularly, indicates the presence of a computer worm:

  • Computer activity that is unusual (messages, sounds, pictures),
  • Automatically starting and running programs
  • System freezes and crashes due to slow computational performance
  • Errors in the operating system and system error messages
  • Without the user's awareness, emails are sent to contacts.
  • Files are missing or have been modified.
  • Warnings from the firewall
  • Strange and unexpected desktop files and icons arise as a result of unusual web browser behavior.

Is Ransomware a Virus?

Ransomware is a type of extortion virus that encrypts your computer and demands payment in order to unlock it. The most common methods to become infected with ransomware are to visit malicious websites, download a malicious file, or install harmful add-ons during downloads. A ransomware attack can be triggered by a single negligent moment. It is difficult to detect an infection because malware is designed to remain unnoticed for as long as possible.

The entire operating system or particular files may be encrypted, depending on the type of ransomware. Following that, the victim is forced to give a ransom.

Malicious malware can corrupt files on the system or reformat the drive. It could potentially remain undetected and communicate with a command and control system, allowing it to participate in a distributed denial of service (DDOS) attack. Furthermore, malware may attempt to capture data such as passwords and keystrokes to documents, which it subsequently sends to a command and control server. When ransomware alerts the system's user that it has been attacked, but only after it has done something to the computer, such as encrypting the drive or files, it is called ransomware. Normally, the message requests money to return the machine to its previous status.

Ransomware is one of the trickiest malware. Prevention and backup are the most effective "treatment" for ransomware. Backups, if any exist, are one technique to recover from this type of ransomware attack. Unfortunately, many people do not have separate backups from the host computer. Backups on a drive attached to a compromised machine would also be vulnerable.

If you see any of the following symptoms, your computer may be infected:

  • Computer performance is slow.
  • Crashing frequently.
  • Unstable computer behavior (a computer sends messages or spam emails without the user's permission, or launches and closes programs without the user's permission, for example).
  • Data loss that hasn't been explained.
  • On your screen, you'll see pop-ups and other messages.
  • Blue screen of death (BSOD).

WannaCry, one of the biggest and most dangerous ransomware outbreaks, happened in the spring of 2017. Approximately 200,000 victims from around 150 countries were asked to pay a ransom in Bitcoin during the cyberattack.

Here are the tips for for ransomware protection:

  • Never click on any untrustworthy links
  • Personal information should not be share
  • Do not open email attachments that appear to be suspicious
  • Never use a USB stick that you don't know
  • Maintain the latest versions of your programs and operating system
  • Use only reliable download sites and On public Wi-Fi networks
  • Use VPN services.

To guard against ransomware, in addition to these infection-prevention methods, it is critical to utilize proper software.

Is Rootkit a Virus?

A rootkit is a sort of software that allows hackers to gain access to and control a computer. It's simple to hide a rootkit's presence once it's been installed, allowing an attacker to keep privileged access while remaining undiscovered.

The terms "root" and "kit" are etymologically related, with "root" referring to the targeted admin account and "kit" to the software components that implement the tool.

Technically Rootkits are a method of deploying malware on a target, rather than malware itself. Rootkits act in a similar style to malware in that they run unrestricted on a target computer, remain undetected by security software and IT managers, and attempt to steal something from the machine. Rootkits pose a threat to endpoint security and must be avoided and addressed.

Although most rootkits attack software and operating systems, some can also infect hardware and firmware on your computer. Rootkits allow hackers to steal personal data and financial information, install malware or utilize computers as part of a botnet to send spam and engage in DDoS (distributed denial of service) attacks after they get illegal access to computers.

Most commonly used rootkits are as follows:

  • Kernel-mode rootkit
  • User mode rootkit
  • Bootkits
  • Firmware rootkits
  • Application rootkit
  • Virtual rootkits.

Rootkits will be used by attackers for a variety of reasons, but the most prevalent is to increase malware's stealth capabilities. It might be difficult to detect the existence of a rootkit on a computer since this type of malware is designed to remain undetected. Rootkit malware can be identified by the following symptoms:

  1. Blue screen

  2. Slow device performance

  3. Web browser behavior that is out of the ordinary

  4. Unauthorized changes to Windows settings

  5. The web pages aren't working properly.

If you believe your computer has been infected with a rootkit virus, shut it down and run a scan from a known clean system. In the case of firmware rootkits, cleanup may require the replacement of hardware or the use of specialist equipment. And reinstalling an operating system is sometimes may be the only option. Also, a memory dump analysis can be an effective strategy in detecting rootkits, too.

Is Trojan a Virus?

A Trojan Horse Virus is a sort of malware that disguises itself as genuine software and installs it into a computer. A Trojan camouflages itself as a legitimate application or file in order to trick you. It tries to get you to download and run malware on your computer. Once installed, a Trojan can carry out the function for which it was created.

An attacker would often employ social engineering to embed harmful code within genuine applications to acquire system access with their program. It is a sort of malware that is usually camouflaged as an attachment in an email or a free-to-download file before being downloaded and installed on the user's device. After being downloaded, the malicious code will carry out the objective for which it was created, such as gaining backdoor access to corporate systems, spying on users' internet activities, or stealing sensitive data.

Because a Trojan horse, unlike computer viruses, cannot appear on its own, it requires a user to download the server-side of the program to function. This implies that for the Trojan to attack a device's system, the executable (.exe) file must be implemented and the application installed. Trojans, unlike computer viruses and worms, cannot multiply themselves.

Because there are numerous types of Trojans, think of Trojans as an umbrella word for malware distribution. A Trojan can operate as a single piece of malware or a tool for various hacking actions, such as delivering future payloads, communicating with the hacker at a later time, or opening up the system to attackers, much like the Greek warriors did from within the Trojan castle. A Trojan is a delivery mechanism used by hackers to transmit a variety of threats, ranging from ransomware that demands money right once to spyware that hides while stealing vital information such as personal and financial information.

Downloading cracked programs, unknown free programs, opening infected attachments, visiting shady websites and any other social engineering that disguises itself by taking advantage of the latest trends can lead to a Trojan infection.

Once a Trojan has infected your device, the most general approach to clear it up and return it to a desirable state is to run a comprehensive system scan using a good quality, automated anti-malware tool. If you're concerned that your device has been infected with a Trojan, you may use a Trojan scanner to check it.

In addition to downloading cybersecurity software, here are a few essential measures to keep oneself safe:

  • Never install or download software from a source you don't trust.
  • Never open an attachment or execute software provided to you by an unknown sender in an email.
  • Keep all of your computer's software up to date with the most recent patches.
  • Make sure your machine has a Trojan antivirus program installed and functioning.

History of Computer Viruses

Viruses have existed for a long time, and nearly all of them were spread via the Internet or its predecessors. According to the National Institute of Standards and Technology(NIST), the first computer virus, known as Brain, was invented in 1986. It was created by two Pakistani brothers and was intended to be used as a copy protection system.

In 1988, The Morris was the first computer virus to propagate widely in the wild. Robert Morris, a Cornell University graduate student, devised it with the intention of using it to compute the size of the internet. His method took advantage of security vulnerabilities in Sendmail and other Unix systems, as well as weak passwords, but it spread too quickly due to a programming error, causing computer processes to be disrupted. It infected around 15,000 workstations in 15 hours, which was the majority of the internet at the time.

The Michelangelo virus was detected for the first time in Australia in 1991. CIH was released in 1998. In 1999, Melissa was released. 2000 was the year of iloveyou. Since the year 2000, there have been so many new viruses released to wreak havoc on the planet that it is impossible to choose the most well-known. With the CryptoLocker malware in 2013, a new type of ransomware emerged. Many new variants of this malware have emerged, including Locky and WannaCry, as well as Petya (not the latest version). In its initial form, the CryptoLocker malware affected over half a million computers.