What You Need to Know About Computer Virus

What You Need to Know About Computer Virus: types, examples, computer virus history, causes and solutions

Computer Virus: types, examples, computer virus history, causes and solutions

Computer virus are extremely harmful and deadly. Here is an article to educate you on What You Need to Know About Computer Virus: types, examples, computer virus history, causes and solutions. Computer owners are so much familiar with the term “computer virus” but are unaware of the causes, types and how to get rid of it.

However, we cannot begin without letting you know the meaning of a Computer Virus.

What is Computer Virus?

A computer virus is a self-replicating program that sometimes spreads by itself into other executable code or documents. Most viruses or worms are malicious programs designed to infect and gain control over vulnerable systems. Computer safety is a good business and every webmaster on the internet should integrate safety tips when using computers

Viruses spread via email can knock out systems burdened by the enormous amounts of generated email, as well as cause individual users major knockouts.

Virus epidemics only infect Microsoft Windows systems, usually through Microsoft Outlook (Express). Most other email clients and operating systems are safe. Runbox recommends using the Run box Webmail interface for reading email, as it prevents automatic execution of possible viruses before they reach your computer. It also strips any malicious scripts from messages so they can’t infect your system (unless you open the original message in a separate window).

READ ALSO: What You Need to Know About Computer Repairs-Detailed Guide

On November 10, 1983, a handful of seminar attendees at Lehigh University, Pennsylvania, USA, heard for the first time the term “virus” applied to computing. The use of the word was strange. The virus that was then on everyone’s mind was the one isolated a few months earlier at the Pasteur Institute in Paris that could be the cause of a new disease called AIDS. In the digital world, talking about viruses was almost nonsense.

The first PC had been launched on the market just two years earlier and only the most technologically informed were running an Apple II computer or one of its early competitors.

However, when on that day the graduate student from the University of Southern California Fred Cohen inserted a diskette into a VAX11/750 mainframe computer, the attendees noted how code hidden in a Unix program installed itself and took control in a few minutes, replicating and spreading to other connected machines, similar to a biological virus.

Cohen tells OpenMind that it was on November 3 when a conversation with his supervisor, Leonard Adleman, led to the idea of ​​giving the name of virus to that code capable of infecting a network of connected computers. The Cohen virus was simple: “The code for reproduction was perhaps a few lines and took a few minutes to write,” says the author. “The instrumentation and controls took almost a day.”

Cohen published his creation in 1984, in an article that began: “This paper defines a major computer security problem called a virus.” But though the extensive research of Cohen and Adleman in the specialized literature would draw attention to their existence, the truth is that before that first virus defined as such appeared, there had already been earlier cases.

In 1971, Robert Thomas, from the company BBN, created Creeper, a program that moved between computers connected to ARPANET and that displayed the message “I’m the creeper: catch me if you can.” According to David Harley, IT security consultant and researcher for the ESET company, “in the research community, we usually consider the experimental program Creeper to be the first virus and/or worm.”

Moreover, a year before Cohen’s seminar, 15-year-old Rich Skrenta developed Elk Cloner, the first computer virus—not named that yet—that spread outside a laboratory. Skrenta created it as a joke for his friends, whose Apple II computers became infected by inserting a diskette with a game that hid the virus.

So, Cohen was not really the first one. But according what computer security expert Robert Slade explains to OpenMind, the special thing in Cohen’s case was not so much his programming as his method. “He was doing the original academic research on the concept; his structure of antiviral software is still comprehensive despite all the developments since.” Cohen also introduced an informal definition of virus: “a program that can infect other programs by modifying them to include a, possibly evolved, version of itself.”

Those first viruses were technological demonstrations. The motivation of their creators was research and their codes were not malicious. Cohen points out that the objective of his program was “to measure spread time, not to attack.” In the case of Creeper, it was about designing a mobile application that could move to the machine where the data resided, instead of going the other way.

As the professor of Computer Science at the University of Calgary (Canada) John Aycock points out to OpenMind, computer viruses were born as “a natural product of human curiosity.” And as such, “their invention was inevitable.”

It was also inevitable that the first malicious codes would soon emerge. In 1986, Brain appeared, a virus created by two Pakistani brothers whose purpose was to punish the users of IBM computers who installed a pirated copy of software developed by them. However, the effects of Brain were slight and the virus included the contact information of its authors so that those affected could contact them and request a cure. Spread by means of diskettes, Brain reached international diffusion, giving rise to the birth of the first antivirus companies.

At the end of the 1980s, codes began to proliferate that erased data or disabled systems. In 1988, the worm created by Robert Morris infected many of the computers connected to the then nascent Internet, especially in research institutions, causing a drop in email services. Its effects were more damaging than anticipated by Morris himself, who became the first person to be prosecuted in the US under the Computer Fraud and Abuse Act of 1986.

In this way, so-called malware began to diversify into different families: worms are programs that move from one computer to another without hiding in another application, while Trojans are harmful programs with an innocent appearance. In 1995, WM/Concept appeared, which infected Word documents. “It opened the door for a plague of document-borne malware that dominated the threat landscape for several years after,” says Harley. The expert lists other typologies that have emerged over time, such as bots that manipulate other people’s systems to launch spam campaigns, send malware or denial of service attacks; or ransomware, codes that hijack a system and force the payment of a ransom, such as the recent case of WannaCry, which in May 2017 infected hundreds of thousands of computers in more than 150 countries.

To this threat landscape we must add the current media, such as social networks, which facilitate the expansion of malware. As explained to OpenMind by Jussi Parikka, expert in technological culture at the Winchester School of Art of the University of Southampton (United Kingdom) and author of Digital Contagions: A Media Archeology of Computer Viruses (2nd ed., Peter Lang Publishing, 2016), “the online platforms for communication and interaction are themselves part of the problem due to their various security issues.”

But despite the many headaches caused by the malware, experts point out that these developments can benefit other technologies. Cohen argues that “benevolent” viruses can, for example, be useful in maintaining and updating systems. “I think artificial life (reproducing programs) still have enormous potential, largely unrealized as of today,” he reflects. “History will tell, but I still hold hope that viral computation will be a benefit to humanity in the future.”

Types and Examples of Computer Virus

Below are the most common types of viruses and other malicious programs;

  • Resident Viruses
  • Multipartite Viruses
  • Direct Action Viruses
  • Overwrite Viruses
  • Boot Virus
  • Macro Virus
  • Directory Virus
  • Polymorphic Virus
  • File Infectors
  • Encrypted Viruses
  • Companion Viruses
  • Network Virus
  • Nonresident Viruses
  • Stealth Viruses
  • Sparse Infectors
  • Spacefiller (Cavity) Viruses
  • FAT Virus
  • Worms
  • Trojans or Trojan Horses
  • Logic Bombs

Like we’ve define above, a computer virus is one type of malware that inserts its virus code to multiply itself by altering the programs and applications. The computer gets infected through the replication of malicious code.

Computer viruses come in different forms to infect the system in different ways. Some of the most common viruses are

Boot Sector Virus – This type of virus infects the master boot record and it is challenging and a complex task to remove this virus and often requires the system to be formatted. Mostly it spreads through removable media.

Direct Action Virus – This is also called non-resident virus, it gets installed or stays hidden in the computer memory. It stays attached to the specific type of files that it infect. It does not affect the user experience and system’s performance.

Resident Virus – Unlike direct action viruses, resident viruses get installed on the computer. It is difficult to identify the virus and it is even difficult to remove a resident virus.

Multipartite Virus – This type of virus spreads through multiple ways. It infects both the boot sector and executable files at the same time.

Polymorphic Virus – These type of viruses are difficult to identify with a traditional anti-virus program. This is because the polymorphic viruses alters its signature pattern whenever it replicates.

Overwrite Virus – This type of virus deletes all the files that it infects. The only possible mechanism to remove is to delete the infected files and the end-user has to lose all the contents in it. Identifying the overwrite virus is difficult as it spreads through emails.

Spacefiller Virus – This is also called “Cavity Viruses”. This is called so as they fill up the empty spaces between the code and hence does not cause any damage to the file.

#File infectors:
Few file infector viruses come attached with program files, such as .com or .exe files. Some file infector viruses infect any program for which execution is requested, including .sys, .ovl, .prg, and .mnu files. Consequently, when the particular program is loaded, the virus is also loaded.

Besides these, the other file infector viruses come as a completely included program or script sent in email attachments.

#Macro viruses:
As the name suggests, the macro viruses particularly target macro language commands in applications like Microsoft Word. The same is implied on other programs too.

In MS Word, the macros are keystrokes that are embedded in the documents or saved sequences for commands. The macro viruses are designed to add their malicious code to the genuine macro sequences in a Word file. However, as the years went by, Microsoft Word witnessed disabling of macros by default in more recent versions. Thus, the cybercriminals started to use social engineering schemes to target users. In the process, they trick the user and enable macros to launch the virus.

Since macro viruses are making a come back in the recent years, Microsoft quickly retaliated by adding a new feature in Office 2016. The feature enables security managers to selectively enable macro use. As a matter of fact, it can be enabled for trusted workflows and blocked if required across the organization.

#Overwrite Viruses:

The virus design purpose tends to vary and Overwrite Viruses are predominantly designed to destroy a file or application’s data. As the name says it all, the virus after attacking the computer starts overwriting files with its own code. Not to be taken lightly, these viruses are more capable of targeting specific files or applications or systematically overwrite all files on an infected device.

On the flipside, the overwrite virus is capable of installing a new code in the files or applications which programs them to spread the virus to additional files, applications, and systems.

#Polymorphic Viruses:
More and more cybercriminals are depending on the polymorphic virus. It is a malware type which has the ability to change or mutate its underlying code without changing its basic functions or features. This helps the virus on a computer or network to evade detection from many antimalware and threat detection products.

Since virus removal programs depend on identifying signatures of malware, these viruses are carefully designed to escape detection and identification. When a security software detects a polymorphic virus, the virus modifies itself thereby, it is no longer detectable using the previous signature.

#Resident Viruses:
The Resident virus implants itself in the memory of a computer. Basically, the original virus program is not required to infect new files or applications. Even when the original virus is deleted, the version stored in memory can be activated. This happens when the computer OS loads certain applications or functions. The resident viruses are troublesome due to the reason they can run unnoticed by antivirus and antimalware software by hiding in the system’s RAM.

#Rootkit Viruses:
The rootkit virus is a malware type which secretly installs an illegal rootkit on an infected system. This opens the door for attackers and gives them full control of the system. The attacker will be able to fundamentally modify or disable functions and programs. Like other sophisticated viruses, the rootkit virus is also created to bypass antivirus software. The latest versions of major antivirus and antimalware programs include rootkit scanning.

#System or Boot-record Infectors:

The Boot-record Infectors infect executable code found in specific system areas on a disk. As the name implies, they attach to the USB thumb drives and DOS boot sector on diskettes or the Master Boot Record on hard disks. Boot viruses are no more common these days as the latest devices rely less on physical storage media.

How To Avoid Email Viruses And Worms
Here are some simple rules you can follow to avoid being infected by viruses through email.

How To Be Safe From Email Viruses And Worms
Here are some simple rules you can follow to avoid being infected by viruses through email.

1. Use a professional, email service such as Runbox. Subscription services provide higher levels of security and support.
2. Make sure that your Runbox virus filter is activated.
3. Use the Webmail interface at www.runbox.com to read your email, or don’t download all your email to an email client unseen. Screen your email first, and delete suspicious-looking and unwanted messages before downloading the legitimate email to your local email client.
4. Make sure your computer has updated anti-virus software running locally. Automatic updates are essential for effective virus protection.

Combined with server-side scanning, you now have two layers of security.
5. Disable message preview in your email client, especially on Windows platforms. Otherwise, malicious programs attached to incoming messages may execute automatically and infect your computer.
6. Ignore or delete messages with attachments appearing to be sent from official Runbox email addresses. Runbox rarely sends email to our users, aside from replies to inquiries and payment reminders. We practically never send an email with attachments to users.
7. Take caution when opening graphics and media attachments, as viruses can be disguised as such files.
8. Maintain several independent email accounts. If a virus infects your only business email address, you’ll be in trouble. Also, keep backups of your most important email and files separately.
9. If any valid message headers of a virus-email indicate what server the message was sent from, contact the service in question and file a formal complaint.

1. Do not open an email attachment unless you were expecting it and know whom it’s from.
2. Do not open any unsolicited executable files, documents, spreadsheets, etc.
3. Avoid downloading executable or documents from the internet, as these are often used to spread viruses.
4. Never open files with a double file extension, e.g. filename.txt.vbs. This is a typical sign of a virus program.
5. Do not send or forward any files that you haven’t virus-checked first.
6. Viruses and spam
7. Virus-makers and spammers often cooperate in devious schemes to send as much spam as possible as efficiently as possible. They create viruses that infect vulnerable computers around the world and turn them into spam-generating “robots”. The infected computers then send massive amounts of spam, unbeknownst to the computer owner.

Such virus-generated email is often forged to appear to be sent from legitimate addresses collected from address books on infected computers. The viruses also use such data, combined with lists of common (user) names, to send spam to huge numbers of recipients. Many of those messages will be returned as undeliverable, and arrive in innocent and unknowing email users’ Inboxes. If this happens to you, use the trainable spam filter to catch those messages.

Signs of Virus Infection

It is vital for any computer user to be aware of these warning signs –

• Slower system performance
• Pop-ups bombarding the screen
• Programs running on their own
• Files multiplying/duplicating on their own
• New files or programs in the computer
• Files, folders or programs getting deleted or corrupted
• The sound of a hard drive


Examples of Computer Virus

Below are examples of computer virus.

Note: Examples of virus is totally different from types.

  • Ransomware
  • Spyware
  • Adware,
  • Trojan horses
  • Keyloggers
  • Rootkits,
  • Bootkits
  • Malicious Browser Helper Object (BHOs)

Causes of Computer Virus and Solutions

Here are some of the primary causes of computer virus infections

  • Suspicious Email Attachments

It’s pretty self-explanatory. Many people make the mistake of opening an email that looks shady just to see what it’s all about. That’s especially true if the Subject Line is very attention-grabbing.  As a business owner, and as a computer user, you should never do that.

If you ever get an email from an unknown source, don’t click on it. Doing so may put your company data at risk. More often than not, computer virus infections are placed in the attachment files. Alternatively, they come in the form of a website/link contained in the email.

  • Removable storage devices afflicted by computer virus infections






In the case of a company, this situation is more common than you’d think. After all, using removable storage devices (like Memory Cards or USB Flash Drives) is very convenient.

However, it’s enough for one of them to have a virus that could possibly infect the entire network.  That’s why you should always check a removable storage device for any signs of a virus infection first. (proper anti-virus software is critical for this).  It’s also important to teach your employees about this safety precaution as well.

Not all people know that computer virus infections can be transmitted through these devices. Taking such a risk just isn’t worth it.

  • Unsecured Internet sources

In this day and age, this is the most common source of computer viruses. It’s very easy to get one if you’re not careful.  All it takes is a simple file download or website click, and you’ve got yourself a virus. That’s why you must make it a priority to teach your employees not to access unsecured websites at work. The best course of action is to filter out the web addresses that would be considered unsafe(a proper firewall with built-in web filtering is important)

The same policies are mandatory for files as well. Only company-approved files should be downloaded. It’s always better to take pre-emptive measures than to be sorry.

How to Get Rid of a Computer Virus

– Computer
– Anti-virus software
– Internet connection
Step 1
If you suspect that you have a virus, launch your anti-virus software and perform a scan of your entire system. If you do not have an anti-virus software application installed on your computer, download one from the Internet. Search for an anti-virus software application with a good reputation. Some anti-virus software applications are bogus and can add viruses to your computer.
Step 2
Wait for the full scan to be completed. Once it has been completed, check to see if it has detected any viruses. If there are viruses, click on the ‘delete’ button on the interface. Sometimes, the virus detected on your computer cannot be deleted by the anti-virus software. When this happens, you have to manually remove the virus from your computer.
Step 3
Take note of the name of the virus detected on your computer. Open a Web browser window and type the name of the virus on the search engine.
Step 4
Read several sources and get information on how to remove the virus. Make sure that you read instructions carefully as manual removal can be tricky. If you do not follow the instructions, you might delete or change some crucial files on your computer.
Step 5
Once you have manually removed the virus from the computer, launch your anti-virus program again and do another scan of the entire system.
Step 6
Wait for the full system scan to finish. Check if you have successfully removed the virus from your computer.
Step 7
If you have not successfully removed the virus from the computer, check the processes running on your computer. You can do this by typing Ctrl+Alt+Del on your keyboard. A window will appear. Click on the ‘Processes’ tab. Scan the list for processes that seem malicious.
Step 8
Search the Internet for the processes and the virus associated with it. Manually remove the virus and perform another system scan.

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