What Is Antivirus Software, and How Does It Work?

Antivirus software helps protect your private data by blocking, detecting, and removing malicious software before it can steal passwords, monitor your activity, encrypt your files, or give attackers access to your device. Modern antivirus tools can monitor computers and mobile devices in real time, scan downloads and email attachments, and warn you about suspicious websites or apps.

The best antivirus software depends on your budget, the devices you want to protect, the features you need, and how much performance impact you are willing to accept.

Below, we explain how antivirus software works, when you may need it, and what to look for when comparing providers.

What is antivirus software?

Antivirus software is a program that looks for malicious code on your device, stops it from running, and removes or quarantines whatever it finds. It works in the background, checking files as they arrive and watching programs for behavior that resembles an attack.

You likely already have some form of it. Windows includes Microsoft Defender, macOS includes Apple's built-in screening tools, and both Google Play and the App Store review apps before listing them. Third-party antivirus adds another layer on top of those protections.

For most people, the real question isn't whether to use antivirus software. It's whether the protection already on the device is enough.

How does antivirus software work?

Antivirus software scans files, apps, downloads, and sometimes network activity for signs of malicious behavior. It can compare files against known malware signatures, analyze suspicious code, and monitor behavior in real time. If it detects a threat, it may block the file, quarantine it, or remove it automatically.

Most antivirus software relies on three main detection methods to identify threats.

• Behavior-based detection: This method watches how a file or program acts after it starts running. If it begins making unauthorized system changes, trying to access sensitive data, or behaving like known malware, the antivirus can flag or stop it.
• Heuristic-based detection: This method looks for suspicious code patterns or file behavior that resemble previously identified threats. It helps detect new or modified malware that may not yet appear in a traditional virus database.
• Signature-based detection: This method compares files against a database of known malware signatures. When a file matches a known pattern, the antivirus identifies it as malicious and can block or remove it.

Many products now combine these methods with cloud-based analysis, sending file details to the provider's servers so a suspicious file can be checked against threats seen on other devices within minutes rather than waiting for the next database update.

What is a false positive?

Sometimes antivirus software incorrectly flags a safe file or app as malicious. This is called a false positive. False positives can happen when a legitimate program behaves in a way that resembles malware, such as making system changes or accessing protected files.

If this happens, first check whether your antivirus software is fully updated. You can also review the alert details, research the file or program from trusted sources, and scan the file with another reputable security tool before restoring or deleting it.

Most antivirus programs also let you whitelist or allow a file that you trust. Only do this when you are confident the file is legitimate, because whitelisting bypasses some protections.

Do I need antivirus software?

Antivirus software can add an important layer of protection for many people, especially if you often download files, install apps from multiple sources, reuse devices for work and personal tasks, or store sensitive information on your device. While built-in protections have improved, dedicated antivirus software may still help reduce your risk from malware, phishing, and unsafe downloads.

Built-in protection isn't always enough on its own. In our survey of 1,000 U.S. adults, people who kept whatever antivirus came pre-installed reported a 42% infection rate, compared with 27% among those who chose a third-party product.

The level of protection you need often depends on your operating system, browsing habits, and how much private information you keep on the device.

Do Windows computers need antivirus software?

Windows devices are frequent targets because of their widespread use. Microsoft includes built-in protections such as Microsoft Defender, but some users may still prefer additional features offered by Windows-specific antivirus, such as advanced phishing protection, identity monitoring, or broader device coverage.

Do Windows 10 computers still need antivirus software?

Windows 10 users have a stronger case for third-party antivirus than Windows 11 users do, and it has more to do with patching than the operating system itself.

Microsoft ended mainstream Windows 10 support on October 14, 2025. It has since extended free Extended Security Updates twice, most recently to October 12, 2027, for devices running version 22H2. Microsoft never formally announced that second extension, and instead added an editor's note to an existing support page. We covered what changed in our guide to Microsoft's extension of Windows 10 security updates.

The security gap between the two versions still shows up in the data. Research from Lansweeper found that Windows 10 devices carry an average of 1,903 active vulnerabilities, compared with 625 on Windows 11, with about two-thirds rated High or Critical. We broke down the findings in Windows 10 carries 3x the security risk of Windows 11.

If you plan to stay on Windows 10, enrolling in the ESU program is the first step. It's free if you sync your PC settings to a Microsoft account, or you can redeem 1,000 Microsoft Rewards points or pay $30 once, and a single license can cover up to 10 devices.

Antivirus software may help catch malware and flag suspicious behavior, but it can't patch the operating system, so it works best alongside ESU rather than in place of it. For device-specific picks, see our guide to the best antivirus for Windows 10.

Do Macs need antivirus software?

Macs have long been viewed as lower-priority targets than Windows PCs, partly because of market share and partly because Apple includes built-in security protections. Still, Macs are not immune to malware, adware, phishing, or malicious downloads.

Apple includes technologies such as XProtect and Gatekeeper to help screen apps and block untrusted software. These protections help, but they don't eliminate every risk.

In fact, Mac users in our survey reported the highest infection rate of any operating system: 44% said a virus had gotten through despite having antivirus installed, compared with 36% of Windows users. Fewer Mac owners run antivirus at all, 78% against 90% of Windows users, which may be part of the picture.

Even on a Mac, additional macOS antivirus software may be useful if you want another layer of protection, especially if you download software outside the App Store or want features beyond Apple’s built-in tools.

Do Android devices need antivirus software?

Android devices can be exposed to malware, unsafe apps, malicious links, and phishing attempts, especially if you install software from outside official app stores.

Google Play Protect helps screen apps in the Google Play Store, but Android users can also sideload apps or install software from third-party websites, which increases risk. Even legitimate-looking apps can sometimes hide harmful behavior.

For added security, some users choose an Android antivirus program, especially if they download files often, use public Wi-Fi, or want anti-theft and web protection features.

Do iOS devices need antivirus software?

iPhones and iPads are generally more locked down than many other devices, which reduces some malware risks.

Apple reviews App Store apps and restricts how apps interact with the operating system, which helps limit traditional antivirus threats.

iOS also uses app sandboxing, which helps keep apps separated from one another. Even so, iPhone users can still face risks such as phishing, unsafe websites, scam messages, and stolen credentials. If you use an iOS security app, it will usually focus more on web protection, breach alerts, or identity tools than on traditional virus scanning.

Do Chromebooks need antivirus software?

Chromebooks can get viruses and other security threats, although they are generally designed with strong built-in protections.

Chromebooks use built-in features such as sandboxing to isolate apps and browser tabs, which can limit the spread of malicious activity. For many users, these protections may be enough, but safe browsing habits still matter.

Do Linux computers need antivirus software?

Linux has a small share of the desktop market, which makes it a less common target for consumer malware. Its permission model also makes it harder for a program to make system-wide changes without explicit approval.

That said, Linux machines can still pass along malware that targets other systems, and servers face a different threat profile than desktops. If you want coverage, see our picks for the best antivirus for Linux.

Is antivirus the same as anti-malware?

People often use the terms anti-malware and antivirus interchangeably, but they differ slightly.

Traditionally, antivirus referred to tools that focused on computer viruses specifically. A virus is a type of malicious program that can replicate itself and spread by infecting other files or systems.

Malware is a broader term that includes viruses as well as spyware, ransomware, trojans, adware, and other harmful software. So all viruses are malware, but not all malware are viruses. In practice, most modern antivirus products are really anti-malware suites.

How does an antivirus prevent malware?

Antivirus software helps prevent malware by combining signature-based, heuristic, and behavior-based detection. Together, these methods improve the chances of catching both known and emerging threats.

Signature-based protection works best when the software is updated regularly, because new threats must be added to the malware database.

Heuristic detection looks for suspicious traits or patterns that resemble malware, even if the exact threat has not been seen before.

Behavior-based protection monitors what a file does in real time, which can help stop threats that would otherwise slip past traditional signature checks.

Can an antivirus prevent ransomware?

Antivirus software can help detect and block some ransomware, especially when it uses updated signatures and behavior-based monitoring. However, no antivirus tool can guarantee complete protection. The best defense against ransomware usually combines antivirus, software updates, safe browsing, and regular backups. 

Using the best antivirus software can improve your protection, but it should be part of a broader security plan.

Can antivirus software prevent hackers?

Antivirus software can reduce some hacking risks by blocking malware, malicious downloads, and suspicious attachments that attackers may use to gain access.

It may also warn you about dangerous files, suspicious links, and infected attachments. Still, antivirus alone cannot stop every type of attack, especially scams that rely on social engineering or stolen passwords.

What antivirus doesn't protect you from

Antivirus software stops malicious code. A lot of what goes wrong online doesn't involve code at all, which is why antivirus works best as one layer rather than a complete defense.

• Phishing and scam messages. If you type your password into a convincing fake login page, no malware was installed. Some antivirus suites add link and site blocking, which may help, but the underlying risk is phishing.
• Weak or reused passwords. A password manager addresses this, and antivirus generally doesn't.
• Data brokers and public records. Much of your personal information is collected and sold legally, which is what data removal services are built to address.
• Unsecured connections. A VPN encrypts your traffic on networks you don't control.
• Breaches at companies you use. Nothing installed on your device can prevent a company from losing your data. Identity theft protection may help you catch the fallout sooner.

Treating antivirus as complete protection is one of the more common mistakes we see, and it's usually where the gaps show up.

Fake antivirus and scareware

One of the more persistent scams is antivirus software that isn't antivirus software at all.

Scareware typically appears as a sudden full-screen browser warning claiming your device is infected, often with a countdown timer and a phone number or download button. The warning itself is the attack. Clicking through may install actual malware, capture your payment details, or connect you to someone posing as tech support.

Real antivirus software doesn't warn you through a web page, and it won't ask you to call a phone number. Legitimate alerts come from software already installed on your device.

If you see one of these warnings, close the browser tab or force-quit the browser, and don't call the number or download anything it offers. Then run a scan with the antivirus you actually installed. Our guides on running an antivirus scan and removing viruses walk through the cleanup.

How to choose antivirus software

When comparing antivirus software, focus on the protections you actually need, the devices you want to cover, and whether the product delivers strong security without slowing your system too much. Some features are essential, while others are optional based on your budget and habits.

1. Scanning: Look for software that offers both real-time protection and on-demand manual scans, so you can check your device whenever needed. Scheduling options are also useful.
2. Detection: Malware detection is the core job of any antivirus product. Independent lab results and review testing can help you compare detection effectiveness.
3. Price and value: Compare plan pricing against the features included, the number of devices covered, and renewal costs after any first-year discount ends.
4. Detection methods: Products that combine signature, heuristic, and behavior-based protection are generally better equipped to catch a wider range of threats.
5. Performance impact: Security software can affect device speed, so it is worth checking testing and reviews for system impact during scans and everyday use.

How much does antivirus software cost?

Antivirus software comes in a wide range of price tiers, from free plans to premium subscriptions with multi-device coverage and added privacy tools. Introductory discounts are common, so it is important to compare both first-year and renewal pricing.

When we reviewed the antivirus market, we found that 64% of top programs cost between $21 and $40 per year. Around 25% cost more than that, and roughly 11% cost less than $20/yr, including a small number that are free. We also found that 93% offer a money-back guarantee of at least 30 days, so you can usually try a paid plan with limited risk.

For current pricing across providers, see our guide to the best antivirus software.

Free vs. paid antivirus

If you use a PC, Windows Defender may be a practical, no-cost option for everyday protection. However, some users may want stronger phishing protection, extra privacy tools, or broader coverage than built-in protection alone provides.

Mac users also benefit from built-in protections such as XProtect and Apple’s malware removal features, which can reduce the need for separate antivirus software in lower-risk situations.

If you want more protection, many providers also offer free antivirus plans. These can help, but they often offer fewer features than paid subscriptions.

The biggest advantage is that you have some kind of protection. The biggest disadvantage is the lack of advanced features. Below are some standard features of most free antivirus software.

Free antivirus features

• Protection from common malware threats, sometimes including ransomware and spyware protection

• Basic device or system tools in some products

• Manual and scheduled device scans

• Malware detection and removal tools

• Limited website or phishing protection in some plans

• Limited network or Wi-Fi protection in some products

While free software can provide a useful baseline, paid plans often include stronger monitoring, broader support, and more advanced protections.

Premium antivirus features

Paid antivirus subscriptions often add features that go beyond core malware detection.

• Email monitoring and filtering
• VPNs
• Phishing and spam monitoring and filtering
• Application control or whitelisting tools
• Ad blockers
• Customer support
• Multi-device coverage

There’s a popular saying in the tech space: if you aren’t paying for the product, then you are the product. As with any security product, it's worth reviewing the provider’s privacy policy, data practices, and reputation before installing free or paid software.

Price matters, but trust and transparency matter too when you are choosing software that may have deep access to your device.

Bottom line

Antivirus software can help protect your private data by detecting threats early, blocking suspicious activity, and reducing the chances that malware can steal information or damage your files.

While no security tool is perfect, antivirus software can be a valuable part of a broader safety strategy that also includes software updates, strong passwords, careful downloading habits, and regular backups.

See our guide to the best antivirus software to help you compare options.

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