How Does a Virus Infect a Computer?

Photo of a virus indication key on a computer keyboard
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When you see a pop-up on your computer coming from your antivirus software that says “virus,” you know that there is some type of issue. However, not all viruses are extremely dangerous, and they are often categorized according to the threat level they carry. Some viruses are simply annoying, but others are quite dangerous. Similarly, some viruses are noticeable, while others will infect your computer undetected.

Keep reading for more information about how to recognize and prevent some of the most common kinds of computer viruses.

What Is a Computer Virus?

A computer "virus" is a simple way of referring to the wide range of software that's designed to spread from computer to computer without the owners' consent or knowledge. These viruses are usually hidden in software, data, or remote drives such as a USB thumb drive.

Viruses also go by a variety of names. One of the most common you'll hear is "malware," which just refers to any malicious software that was designed to do harm. Malware can be further broken down by definitions such as a "trojan horse," which is when malware pretends to be safe software so that users willingly allow it to access their hard drives. "Worms" are pieces of malware that specialize in replicating themselves and spreading, usually through networks. "Spyware" lurks unnoticed and tracks sensitive information such as keystrokes, or it secretly takes screenshots to send to the hacker.

"Adware" refers to software that causes pop-ups and banners. As any internet user can tell you, pop-ups and banners are commonplace online. That's an example of how not all viruses are equally bad. Adware can be used legally as a benign addition to freeware, but it can also be used maliciously by bad actors.

How Do You Know If There Is a Virus?

If you are using a computer that has the most current version of a reputable antivirus program, it should know when there is a virus on the computer. It may even be able to warn you if you are about to download one.

Antivirus software usually runs regular scans automatically, but you can trigger a scan manually if you have reason to believe you have a virus.

Even if you don't have an antivirus program installed on your computer (and you should), there are tell-tale signs that will let you know you may have been infected by a virus. These signs include:

  • Slow performance or frequent crashes
  • Excessive pop-ups
  • Becoming locked out of your files or programs
  • A new homepage or other changes to your browser
  • Emails sent from your accounts without your knowledge
  • Unknown programs on your computer
  • Short battery life
  • Disabled security software

How Do You Stop and Prevent Viruses?

Every antivirus program is different, but most of them will automatically quarantine or remove any viruses they find. Sometimes, antivirus software may ask for your permission to delete the suspected virus. It is a good idea to take a look at the file, as sometimes the program may consider a legitimate file a virus and attempt to delete it. The quarantine feature allows the computer’s owner to either restore the file or remove it.

How to Prevent Virus Infection

If you don't have a computer virus and you want to keep it that way, there are some basic preventative measures you can take. First and foremost, scan for viruses, and make sure these viruses are scheduled regularly.

If you can run a quick scan every day and a deep scan once a week, that should be enough to catch most viruses.

Make sure that you use the antivirus program’s settings to schedule automatic downloads and updates. You should also update any other software you have on your computer. Companies regularly update their software and programs to fix security flaws. Failing to keep up with these updates can leave you vulnerable to hackers.

Instruct your email program to let you know if you are about to download a file or picture. If possible, change your email settings to only display plain text. That way, your email provider should prompt you before downloading any links or pictures that may be contained within the message.

Do not ever click on a link or attempt to download a file from an email address that is unfamiliar to you. If the temptation is too great and you want to follow the link, browse for the page on a search engine instead of following the link directly. You can also use online resources to check for previous reports of malware from the link.

The Bottom Line

Technology does not have to be overwhelming or scary, but if you want to keep your information safe, technology does force you to increase the amount of security you use. Remember, there are bad actors out there who are doing all they can to access your data and obtain your personal information. In response, you should always be proactive when keeping your security measures and antivirus software up-to-date.

Article Sources

  1. Dell. "What Are the Different Types of Viruses, Spyware, and Malware That Can Infect My Computer?" Accessed March 22, 2020.

  2. Norton AntiVirus. "What Is a Computer Virus?" Accessed March 22, 2020.

  3. Cybersecurity and Security Infrastructure Administration. "Understanding Anti-Virus Software." Accessed March 22, 2020.

  4. Norton AntiVirus. "Virus Warning Signs: How to Tell If Your Computer Has a Virus." Accessed March 22, 2020.

  5. McAfee. "Why Software Updates Are So Important." Accessed March 22, 2020.

  6. Norton AntiVirus. "Is This Website Safe." Accessed March 22, 2020.