What Is a Computer Virus and How Does It Work?
Learn what a computer virus is, how it works, what common types to watch out for, and how to defend against them in this complete guide.
Top-rated free antivirus now with online scam and malware protection
Join millions of others using our free antivirus. Boost your defense against today’s cyberthreats. Get AI-powered anti-scam guidance from our new Avast Assistant, plus protection against scams.
Also available for Mac, Android, and iOS
Also available for PC, Android, and iOS
Also available for Mac, Android, and PC
Also available for PC, Mac, and iOS
January 2025
Top Rated Product 2024
Top Rated Product 2024
January 2024
Best Protection
Best Protection
Get AI-powered anti-scam guidance
Block hidden web scams
Easy to install, effortless to use
Millions of users worldwide
January 2025
Top Rated Product 2024
Top Rated Product 2024
Get it for free!
Free download
Free download
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Get free antivirus that comes with advanced privacy and security tools
Avast Free Antivirus is more than just an antivirus — it also includes these specialist tools. Plus, use our new Avast Assistant’s real-time guidance against potential scams.
Get anti-scam guidance, powered by AI
Decide if online messages or offers are scams, supported by our Avast Assistant’s real-time guidance about suspicious online messages, offers, and more.
Easy to install and use
It only takes a moment to install Avast Free Antivirus and once it’s done, it’ll run quietly in the background, helping to protect you against viruses and other malware in real time, 24/7.
Wi-Fi network security
Connect more safely to any Wi-Fi network, even unsecured public networks, plus see who’s using your home Wi-Fi and help block intruders with a click.
Protection against ransomware attacks
Help protect your information. Don't let your personal photos, files, and documents fall victim to hackers using ransomware.
Enhanced digital security for PCs, macOS, and mobile devices
Want to feel more confident in your digital world?
Use our automatic cybersecurity shields against viruses, ransomware, zero-day threats, and other types of malware.
Plus, we can also help you to:
Use our automatic cybersecurity shields against viruses, ransomware, zero-day threats, and other types of malware.
Plus, we can also help you to:
New: Get AI-powered anti-scam guidance fast with Avast Assistant.
Block scam websites and emails to stay away from them, backed by AI.
Protect your personal data and webcam from hackers.
Choose a VPN for more online privacy
Help block ISPs from tracking your activity, help avoid geo-restrictions from content providers, and ensure public Wi-Fi is safer with Avast’s Virtual Private Network (VPN).
Enjoy more storage space and a faster device
Reclaim gigabytes of storage space and get your device working like new by removing junk like leftover files, bloatware, and unwanted programs. Avast Cleanup also updates your software automatically, hibernates resource-draining apps, and more.
It’s so easy to install — switching to Avast takes seconds
You can start using Avast’s award-winning antivirus immediately. It’s quick and easy to install, and gives you all the protection you need to live your online life securely. And it’s totally free — so give it a try right now.
Avast has hundreds of millions of users worldwide
I have used Avast for a few years. The protection is the best for the money. I also cover my phones with Avast and I haven’t had any problems yet.
Carol J.
2023-09-12
I have used Avast for many years. The reason is very simple: you offer a great free version that actually works. This lets me afford the other amazing services you offer when needed, like Avast Cleanup.
James M.
2023-08-29
I've used Avast Free Antivirus on my computers, tablets, and smart phones for many years. It updates frequently and automatically. It automatically scans and protects me from malicious web sites. It does what I need. What more could I ask?
OB
2023-06-10
“The well-known security specialist Avast received a total of three awards for its outstanding performance ... shows how reliably and securely the security software renders its service...”
Awarded Top-Rated Product 2023
by AV-Comparatives
by AV-Comparatives
Get privacy and performance tips, straight from the experts
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What Is Hacking?
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What Is the Dark Web and How to Access It?
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How to Clear the Instagram Cache on Your Device
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How to Identify WhatsApp Scams
Learn to spot WhatsApp scams and fraudsters by recognizing the red flags and scam types.
Block Mobile Scams Instantly with AI-Powered Scam Guardian Pro
Block scam calls, texts, and phishing emails before they reach you. Avast Scam Guardian Pro delivers real-time AI protection in one easy app for complete mobile security.
Keeping people around the world safer & more secure
Using real-time intelligence from hundreds of millions of Avast users, we prevent more than 66 million threats every day.
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