The fastest way to stop a virus is to prevent it from getting in

Most viruses arrive through email attachments, downloads from untrusted websites, or links in messages that look legitimate but are not. You stop them before they run by keeping your operating system and software patched, running antivirus software that scans files before they execute, and not opening attachments or clicking links from people you do not know. If a virus is already on your machine, antivirus software can remove it — but prevention is faster and cheaper than removal.

The three layers that work are: keeping your system updated so attackers cannot use known holes, using antivirus software to catch what gets through anyway, and changing your own behaviour so you do not hand the virus a way in. All three matter. Skipping any one of them leaves you exposed.

Key Takeaways

  • Turn on automatic updates for your operating system and all installed software so security patches arrive without you having to remember.
  • Install antivirus software from a known vendor — Windows Defender comes free with Windows, and Malwarebytes is a low-cost option for additional scanning.
  • Do not open email attachments from people you do not know, and do not click links in unexpected messages even if they appear to come from your bank or a service you use.
  • If your machine is already infected, run a full system scan with your antivirus software in Safe Mode, where fewer programs load and the virus has less to hide behind.

Keep your operating system and software patched

Every month, Microsoft releases patches for Windows, and Apple releases them for macOS. These patches close holes that viruses and other malware use to get in. If you do not install them, you are leaving the front door unlocked.

Turn on automatic updates so patches arrive without you having to check. On Windows 10 and 11, go to Settings, then Update & Security, then Windows Update, and make sure "Automatically read and install updates" is on. On macOS, go to System Settings, then General, then Software Update, and turn on "Automatic updates". Your browser — Chrome, Firefox, Edge, or Safari — also updates itself automatically if you leave it running and restart it occasionally.

The same applies to other software you use often. Adobe Reader, Java, and older versions of Flash were common entry points because they had known holes and many people did not update them. Most modern software updates itself automatically now, but check the settings in any program you use daily.

Install and run antivirus software

Antivirus software watches files as they arrive and as programs try to run them. It compares what it sees against a database of known viruses and against patterns that look like virus behaviour. If something matches, it stops the file from running and puts it in quarantine — a locked folder where it cannot hurt your machine.

Windows Defender comes built into Windows 10 and 11 at no cost. It runs in the background automatically and catches most common viruses. If you want a second opinion or more aggressive scanning, Malwarebytes offers a free version that scans on demand and a paid version that watches in real time. Both work alongside Windows Defender without conflict.

On macOS, the built-in XProtect scans files as they arrive. It is less visible than Windows Defender but runs the same way. If you want additional scanning, Malwarebytes also makes a macOS version.

Run a full system scan once a month or whenever you suspect a problem. This takes an hour or more but checks every file on your drive. Do this in Safe Mode — restart your machine and hold Shift (Windows) or Command-R (Mac) during startup — because Safe Mode loads only essential programs, and viruses have fewer places to hide.

Recognize and avoid common infection routes

Viruses need you to run them. They arrive as email attachments, as downloads from websites, or as links in messages. The attacker's job is to make you think the file is safe or that opening it is urgent.

Do not open attachments from people you do not know, even if the message looks professional. Banks and payment services never ask you to read something to verify your account. If you get a message claiming to be from your bank with an attachment, it is not from your bank — call the number on your card instead.

Be suspicious of unexpected attachments even from people you do know. If a friend sends you a file you did not ask for, message them separately (not by replying to the email) and ask whether they meant to send it. Their email account may have been hacked.

Downloads from the official app store for your device — the Microsoft Store, Apple App Store, or Google Play — are scanned before they go live. Downloads from random websites are not. If you need software, search for the official website of the company that makes it, not a third-party read site.

What to do if your machine is already infected

If your antivirus software has flagged a virus, or if your machine is running slowly, freezing, or showing pop-ups you did not click, run a full system scan in Safe Mode. Restart your machine, hold Shift during startup (Windows) or Command-R (Mac), and let your antivirus software scan every file.

If the scan finds and removes the virus, restart normally and run the scan again to make sure it is gone. If the virus comes back or if your machine still behaves strangely after removal, the infection may be deeper than antivirus software can reach. At that point, backing up your important files and reinstalling your operating system is faster than trying to clean it manually.

If you cannot back up your files because the machine will not start, take it to a repair shop. They have tools to recover your data and clean the machine without running the infected operating system.

find your email and messaging accounts

If a virus steals your email password, it can send messages to everyone in your contacts with infected attachments, making them think the virus came from you. Protect your email by using a strong password — at least 12 characters, mixing letters, numbers, and symbols — and by turning on two-factor authentication.

Two-factor authentication means that even if someone gets your password, they cannot log in without a code from your phone. Gmail, Outlook, and Yahoo all offer it. Turn it on in your account settings under Security.

The same applies to any account where you store files or make payments. A compromised account is how viruses spread to other people and how attackers steal money.

Use a firewall

A firewall is software that watches network traffic — data coming in and going out of your machine. It blocks connections from programs you do not recognize and from outside sources trying to reach your machine without permission.

Windows Defender includes a firewall that is on by default. macOS has one too. You do not need to install a separate firewall unless you are running older software or have specific security needs. The built-in firewall is enough for most people.

Frequently Asked Questions

Can a virus infect my machine if I never open email or read files?

Viruses can arrive through websites you visit, through USB drives you plug in, or through network connections if your firewall is off. Email and downloads are the most common routes, but not the only ones. Keeping your system patched and running antivirus software protects you even if you are careful about what you open.

Is antivirus software slowing down my computer?

Antivirus software uses some processing power, but modern versions are designed to run in the background with minimal impact. If your machine is very slow, the problem is more likely too many programs running at startup, a full hard drive, or an infection that is already there. Check your startup programs in Settings and uninstall software you do not use.

Do I need antivirus software if I only use my phone?

Phones running iOS or Android have built-in protections that are stronger than Windows or macOS. The app stores scan everything before it goes live. You still should not open links from strangers or read apps from outside the official store, but a separate antivirus app is not necessary.

What is the difference between a virus and malware?

A virus is a type of malware — malware is the umbrella term for any software designed to harm your machine or steal your data. Viruses copy themselves and spread to other machines. Spyware watches what you do. Ransomware locks your files until you pay. Antivirus software catches all of them the same way: by recognizing their patterns and stopping them before they run.

If I reinstall Windows, will that remove all viruses?

Yes. Reinstalling your operating system erases everything on your drive and replaces it with a clean copy. Before you do this, back up your important files to an external drive or cloud storage. Some viruses can hide in the backup, so scan the backup with antivirus software before you restore files to the new installation.