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What is a computer virus? Definition & how they work

A young woman sitting at a laptop, reading an article about what computer viruses are

Computer viruses can pose a significant, often undetectable, threat to your online safety. That’s why safeguarding your devices during your online ventures is a fundamental aspect of maintaining digital security. Learn about viruses, how they work, and how strong online security technology can help prevent infections and keep you safer online.

Definition of computer virus

In simple terms, a computer virus is a malicious code or program designed to spread from one computer to another, similar to how a flu virus spreads from host to host. In today's digital age, the term "computer virus" is widely known and associated with potential harm and security risks. Just as typical viruses require a host cell to reproduce, computer viruses cannot spread and infect without attaching themselves to files or documents.

When a virus infects your computer, it can cause unexpected and damaging effects, such as corrupting or destroying data and harming the system software.

Also, find out which types of computer viruses exist in another blog article.

How does a computer virus work?

A computer virus works by inserting or attaching itself to a legitimate program or document that supports macros. Once the virus has successfully attached, it lies dormant until certain conditions trigger its execution. Once a virus has infected a program, file, or document, it remains inactive until the infected program is run. When you implement the infected program, the virus code is activated, allowing it to carry out its intended actions. It's worth noting that a virus can often infect and stay hidden without showing apparent signs or symptoms on your computer.

Once a computer is infected with a virus, it can potentially spread to other computers on the same network. The dangers of a virus can range from stealing passwords and data, logging keystrokes, and corrupting files to spamming your email contacts and even taking control of your entire machine. Some viruses are designed with the intention of causing financial harm, making them even more dangerous.

Norton offers comprehensive antivirus and other security tools to safeguard your computer from viruses, malware, worms, and other online threats. Learn more about which antivirus solution suits you.

How do computer viruses spread?

Computer viruses can spread through various means, and knowing how to contract a virus is essential. Here are some common methods of virus transmission:

  • Email attachments and text messages: Viruses can be disguised as attachments in text or email messages. Opening these text or email attachments can initiate the virus and infect your computer.
  • Internet file downloads: Downloading files from untrustworthy websites or clicking on suspicious links can expose your computer, hard drive, and operating system to viruses. Always be cautious when downloading files from the internet.
  • Social media scams: Virus-laden links can be disguised as attractive or intriguing content on social media platforms. Clicking on these links can lead to viruses or malware.
  • Mobile devices and smartphones: Mobile devices are not immune to viruses. Questionable app downloads can infect your mobile device with viruses.
  • Disguised file attachments: Viruses can be hidden within seemingly harmless files, such as images, greeting cards, or audio and video files. Exercise caution when opening files from unknown sources to avoid inadvertently allowing malicious code onto your computer.

How to know if you have a computer virus?

Detecting a computer virus can be tricky because they often try to stay hidden. However, some signs may indicate your computer is infected and reveal what viruses can do to your computer:

Signs of a potential computer virus infection:

  • Sluggish performance: If your computer's once nimble operations suddenly devolve into a crawl, with tasks taking longer than usual, it could signal a lurking virus exploiting your system's resources, sapping its speed and responsiveness.
  • Unwanted pop-ups or messages: An influx of persistent pop-up ads or error messages disrupting your digital experience might indicate the infiltration of malware.
  • Frequent crashes or freezes: Should your computer become prone to frequent crashes or unexplained freezes, the presence of a virus could be the culprit, orchestrating disruptions that interrupt your workflow and undermine your productivity.
  • Browser changes: Witnessing unauthorized alterations in your web browser's settings or an unexpected shift in your homepage points to potential viral interference. A virus or other malware might be manipulating your online activity, infringing on your digital autonomy.
  • Missing or corrupted files: The sudden disappearance of files or the discovery of corrupted data can be indicative of a virus's destructive capabilities. Viruses can erase or manipulate files, resulting in data loss or software malfunctions that hinder your system's functionality.
  • Strange network activity: Unexpected surges in your internet usage could be an ominous sign of a virus utilizing your network to connect with its command server. This clandestine network activity underscores the need for swift and thorough investigation.
  • Disabled security software: Some cunning viruses incapacitate your antivirus software, rendering it powerless against their onslaught. If you find your security software mysteriously deactivated, exercise caution as your system could be exposed to grave risks.
  • High CPU usage: Delving into your computer's Task Manager (or Activity Monitor on macOS) and encountering abnormally high CPU usage may mean that a virus is surreptitiously operating in the background. Elevated CPU usage can indicate a virus executing malicious processes beyond your view.

If you notice any of these warning signs, it's essential to act quickly to identify and remove the virus. Get Norton AntiVirus Plus to run a full system scan to help identify and root out any viruses or other malicious code. 

How to prevent computer viruses?

In the digital landscape, safeguarding against computer viruses is paramount to protecting your devices and sensitive data. While traditional antivirus software plays a role, a comprehensive security approach is crucial for robust protection against various malware threats, including viruses. You can help strengthen your defence by using strong passwords, updating software, and avoiding suspicious links. 

Get ironclad virus protection

Known for its multi-layered defence mechanism Norton AntiVirus Plus functions as a solution against online threats. By integrating advanced, patented technologies, Norton AntiVirus Plus cleverly fends off online threats, performs thorough scans for potential malware, and helps providing your system with continuous, unobtrusive updates. These proactive measures help ensure users are protected from both common and emerging threats and stay one step ahead of malicious intent.

However, implementing a security tool is only one piece of the puzzle. It is also important to extend protection to all internet-connected devices - be they smartphones, tablets, or other IoT devices. Collective vigilance against online threats can be supported by routine software updates, creating robust, unique passwords and using discretion when interacting with online links or downloads.

In essence, understanding the intricacies of computer viruses and how they operate is the foundation of digital security. By combining prudent online practices with powerful security solutions like Norton AntiVirus Plus the risk of viruses and other malicious threats drops dramatically. In our ever-evolving digital age, protecting yourself is not just an option - it's recommended.

Practicing safe browsing habits is crucial for preventing computer viruses. Explore this comprehensive list for more information on avoiding viruses and infected files.

Emma McGowan
  • Emma McGowan
Emma McGowan is a privacy advocate & managing editor at Gen, formerly a freelance writer for outlets like Buzzfeed & Mashable. She enjoys reading, sewing, & her cats Dwight & Poe.

Editorial note: Our articles provide educational information for you. Our offerings may not cover or protect against every type of crime, fraud, or threat we write about. Our goal is to increase awareness about Cyber Safety. Please review complete Terms during enrollment or setup. Remember that no one can prevent all identity theft or cybercrime, and that LifeLock does not monitor all transactions at all businesses. The Norton and LifeLock brands are part of Gen Digital Inc. 


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