What Is a Computer Virus?

What you need to know about the types of computer viruses

A computer virus is a type of program that, much like a regular virus, attaches itself to a host with the intention of multiplying and spreading its infection further. Computer viruses can be created by anyone with the proper skill set, from individuals to major organizations, and can infect computers, smartphones, tablets, and even smart cars.

Computer Virus Definition Confusion

The term "computer virus" is often used incorrectly as an umbrella term to refer to all suspicious programs, plugins, or code that infect software, computers, and files. This misuse of the phrase is likely due to it being so well-known by the general population due to its frequent use in TV shows and movies such as the Star Trek and Terminator franchises.

In reality, the correct umbrella term for such malicious software is malware, of which the computer virus category is just one type.

Other types of malware include spyware, worms, and Trojans.

Basically, computer viruses are a kind of malware that install themselves on a device and multiply.

Some viruses are designed to steal or corrupt data while others are created to destabilize a program or system and potentially make it unusable. Others are simply made for fun by the programmer and may just display an image or text message after a computer is turned on or an app is opened.

If the malware that’s infected a host hasn’t been designed to multiply and spread, it technically isn’t classified as a computer virus regardless of how dangerous it is.

Different Types of Computer Viruses

The many different types of viruses are usually categorized by what they target and how they function, rather than their creation process and coding style. Many computer viruses can fall under more than one category.

Here are some common computer virus examples:

  • Browser hijacker viruses: These computer viruses infect your web browser and are often used to change your Home page, steal data, and display ads.
  • Boot sector viruses: These are known to affect disks used to assist in a system boot up in addition to the boot sector of the hard drive.
  • Direct action viruses: These viruses are activated by opening a downloaded file or program.
  • Email viruses: These emails are designed to multiply by attaching themselves to emails, generating emails by using your address book, or infecting the email app with the intention of stealing data.
  • Macro viruses: Macro computer viruses are coded in a macro language so that they can be attached to documents and activated as soon as the file they’re attached to is opened.
  • Polymorphic viruses: A type of computer virus that can change itself to evade detection by security systems and anti-virus programs.
  • Resident viruses: Resident viruses infect an operating system and continuously run in the background negatively affecting system and app performance.
  • Non-resident viruses: These type of viruses shut down after performing their task.

How to Tell If Your Computer Has a Virus

While many computer viruses can remain well-hidden on your device, there are several clear behaviors that could suggest you’ve fallen victim to an infection, such as a noticeable decrease in system speed, changes being mysteriously made to system and app settings, notifications for services and apps that you don’t own, browser extensions or plugins being installed without your permission, and an inability to go online or open some programs.

How to Protect Your Computer From Viruses

It’s important to practice a variety of strategies to keep your computer and other smart devices safe from viruses and other forms of malware.

Here are some of the best ways to protect your computer.

  • Keep operating system and apps up-to-date: This will make it harder for viruses to infect your devices.
  • Only connect to trusted internet connections: This can also protect you from other types of attacks such as ARP spoofing.
  • Avoid suspicious attachments: Never open email attachments from unknown senders, as these can contain malware and other viruses.
  • Only download files from official websites and trusted sources: Downloading files from websites you're unfamiliar with is always a risk. No matter how legitimate a download may seem, if it's not from a well-known source, avoid it.
  • Install antivirus software: A quality antivirus package will help you get rid of a virus on your computer and protect you from future infections.

Computer viruses can be frustrating, and in a worst case scenario, incredibly dangerous. However, it is possible to protect yourself against them by taking the right precautions and, if you need to, deal with them if your devices ever get infected.