What is antivirus software? Antivirus definition

Man using mobile device to learn about how to protect himself from cyber threats with antivirus software.

Antivirus software searches for known threats and monitors the behavior of all programs. It seeks to block or remove malware as quickly as possible. If you don’t have antivirus software installed, you could be at risk of picking up a virus.

Antivirus software helps protect your computer against malware and cybercriminals. Antivirus software looks at data — web pages, files, software, applications — traveling over the network to your devices. It searches for known threats and monitors the behavior of all programs, flagging suspicious behavior. It seeks to block or remove malware as quickly as possible.

Antivirus protection is essential, given the array of constantly-emerging cyberthreats. If you don’t have protective software installed, you could be at risk of picking up a virus or being targeted by other malicious software that can remain undetected and wreak havoc on your computer and mobile devices.

If you already have antivirus software, you may believe you’re all set. But it might not be that simple. With new and savvier cyberthreats and viruses surfacing, it’s important to stay current with the latest in antivirus protection.

If there’s any crack in your cybersecurity defenses, cybercriminals likely will try to find a way in. Ensuring your antivirus software is up and running, and up-to-date, is a good place to start. However, hackers, scammers, and identity thieves are constantly tweaking their methods, so it’s a good idea to get protection from a comprehensive security solution.

What is antivirus software designed to do?

What exactly is antivirus software designed to do? We’re talking about a program or umbrella of programs whose purpose is to scan for and eradicate computer viruses and other malicious software, also known as malware. Antivirus software is a vital component of your overall online and computer security strategy in its protection against data and security breaches along with other threats.

When looked at simply, a computer virus is similar to a cold virus. It’s designed to go from one computer or device to the next, copying itself, and spreading malicious codes and programs that can damage and infiltrate your operating systems. Viruses are designed to give criminals access to their victims’ devices.

These viruses, spyware, and other malicious software are known as malware, and can be surreptitiously installed on your computer or device. Malware can do everything from crashing your device to monitoring or controlling your online activity. This control may enable hackers to send spam and steal your private information, which could eventually lead to identity theft.

Antivirus software provides protection against these types of threats by performing key tasks:

  • Pinpointing specific files for the detection of malicious software
  • Scheduling automatic scans 
  • Scanning either one file or your entire computer at your discretion
  • Deleting malicious codes and software
  • Confirming the safety of your computer and other devices

As cybercrime evolves and becomes more sophisticated, whether it’s your own PC or other devices on a larger network, you don’t want to leave yourself or your network vulnerable. If you don’t have security software, you could be opening the door for cybercriminals to gain access to your most sensitive information — and potentially garner control over your computer and mobile devices.

What are the different types of antivirus protection?

Several types of antivirus programs have evolved over the years. When setting up your umbrella of protection, it’s important to understand the more common antivirus programs available.

Malware signature antivirus

Malware, or malicious software, installs viruses and spyware on your computer or device without your knowledge. Malware can steal your login information, use your computer to send spam, crash your computer system, and essentially give cybercriminals access to your devices and the information stored on them, and even the ability to monitor and control your online activity.

Malware signature antivirus software detects malware signatures, which are digital fingerprints of malicious software. Antivirus protection can scan for specific malicious codes, identify specific viruses, and disable these programs.

While malware signature antivirus protection is key for detecting and eradicating known viruses, one limitation is its inability to address new viruses. The antivirus product simply doesn’t contain these new virus signatures.

System monitoring antivirus

This is where system monitoring antivirus software comes into play. This antivirus protection can monitor software and computer systems for behavior that is suspect or atypical of the user.

For instance, alerts are created when a user connects to unfamiliar sites or attempts to access a large number of files, or when there’s a significant increase in data usage.

Machine learning antivirus

Another form of protection can be machine learning techniques, which monitor “normal” computer or network behaviors. The machine learning antivirus software is able to limit activities by programs or computers if they look suspicious.

More specifically, machine learning detection implements algorithms to facilitate malware detection that is broader in scope. This type of antivirus protection is beneficial because it works in tandem with other antivirus applications to provide multiple layers of protection.

One example of machine learning is the design of Microsoft’s latest antivirus software, which can gather data from more than 400 million computers running on Windows 10 to discover new malware. (Note: To be clear, this is diagnostic data that a consumer can opt out of reporting.) This, in turn, takes us back to the importance of signatures, as this intelligence will allow for the development of new signatures for the latest malware discovered. This automation is key in its ability to stay on top of the latest viruses.

What does antivirus software help protect us from?

The beauty of malware for hackers is its ability to gain access to or damage a computer without our knowledge. It’s important to be aware of the many different types of malicious codes, or “malware,” against which antivirus software is designed to protect:

  • Spyware: stealing sensitive information
  • Ransomware: extorting money
  • Viruses
  • Worms: spreading copies between computers 
  • Trojans: promising one thing but delivering another 
  • Adware: advertising
  • Spam: spreading unwanted email

Isn’t Windows Defender enough?

Starting with Windows 8, Windows has built-in antivirus protection known as Windows Defender that is enabled by default. But is it enough? The answer is “maybe” in that its efficacy isn’t certain due to its reliance on several moving parts.

For instance, Windows Defender is a good defense against traditional viruses. But it may not detect threats beyond regular viruses, and may not protect your devices against more sophisticated infiltrations such as ransomware. So its effectiveness also depends on how careful you are as an individual. Are you going to click on that link or email attachment from an unknown sender or website? In order to be safe, you likely need an added layer of protection.

Do I need antivirus protection for Mac?

While Macs and other Apple devices may not be as frequently targeted as Windows computers, it’s still a good idea to get additional antivirus protection to be ready for what may come in the future. At the moment, if you’re careful about what you open, don’t click on unknown links or attachments, and are careful in your online activity, you may be safe. But is it an unknown risk you’re willing to take? “Safe for now” may transition to “no longer safe.”

Free antivirus software: Does it work?

Another common question is whether free antivirus software protects us. But is anything ever really free? “Free” antivirus inevitably supports and makes money with advertising and tracking, and by installing junkware.

Free downloads also can hide malware. If you go this route, only download software from sites that you absolutely trust. You also must ensure that your security setting is set high enough to detect malicious codes.

Another thing to keep in mind when considering whether to rely on free antivirus protection? Identity theft protection, mobile security, and data security support options. These important security features often are lacking with free software.

Sign up for Norton 360 today

Considering all of the risks mentioned above, third-party antivirus protection can be critical. It can mean the theoretical difference between browsing online safely — with your financial and personally identifiable information (PII) safe inside your lockbox at home, and going shopping with your personal and financial information available for the taking.

Norton 360 features top-of-the-line defenses against these cyber threats, safeguards your PII and online transactions, and ensures emails and links come from trusted sources. Don’t leave your cybersecurity up to chance; sign up for the latest in antivirus protection.

It's smart to remember that antivirus software alone isn’t enough to protect against cyber threats. Cyber Safety also means protecting not only your devices, but also your identity and privacy.

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Alison Grace Johansen
  • Alison Grace Johansen
  • Freelance writer
Alison Grace Johansen is a freelance writer who covers cybersecurity and consumer topics. Her background includes law, corporate governance, and publishing.

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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