Windows viruses are a huge problem, and if you step into the online world without adequate protection you have only yourself to blame should your PC stop working properly and your personal data fall into the wrong hands.
There is really no excuse for not running antivirus software when there are so many good, free options out there. We've rounded up six of them to help you make an informed decision.
Should you get free antivirus?
With several huge malware and ransomware attacks making the headlines over the past couple of years, no-one should be under the illusion that they can get away without running any antivirus software. Since it doesn't have to cost any money, there's really no excuse.
While free antivirus doesn't always offer the most complete protection it's better than having none at all and free versions often use the same antivirus 'engine' as their paid-for products.
And where we talk about complete protection, we mean that free versions tend not to include any of the extra features you'd find in a paid-for internet security suite. These can include specific protection from ransomware as well as spam filtering, parental controls, password managers, VPNs and cloud storage.
If you want the extra features that a paid-for version includes, you'll find recommendations in our best antivirus roundup.
Is free antivirus really free?
Yes it is. But you may well trade off some privacy. For example, Avast and AVG’s privacy policies clearly explains how it uses your personal and non-personal information when you download and use its free product.
With Avast in particular, you're asked if you want to opt in to data collection during installation. This is why it is absolutely crucial you read what you're agreeing to when you install an app, and are extra careful to opt out of any data sharing.
Otherwise, you grant the software the right to share some of your (anonymised) information to third parties, which may include advertisers and other companies.
The danger is that a company might work out how to de-anonymise this data, which is a risk you don't want to take.
And some free antivirus products will be supported by adverts, typically on Android versions. You can find out if it's worth installing antivirus on Android and whether iPhones need protecting from malware or not.
And these days, antivirus software should comply with GDPR in Europe and with other privacy regulations in other countries.
Does free antivirus software work?
Privacy is perhaps not the most important factor, depending on your outlook. Antivirus software is designed to prevent your PC and laptop - plus phone and tablet - from being infected by malicious code which could cause issues ranging from annoying pop-ups through to stealing your personal information or even deleting or encrypting your files.
The effectiveness of antivirus software changes over time, and a product that stops all viruses today may not do that tomorrow or in a month. No antivirus software offers a cast iron guarantee that it will stop 100% of malware, but many achieve this figure. And it's essentially the same virus protection you get from the paid-for version of that product.
Again, though, remember that the protection only goes so far. If you want the best protection against the widest range of threats, pay for an internet security suite.
Best Antivirus software reviews
Avira Free AntiVirus
Avira is a very strong contender in the free antivirus space, and this is one of the best specified free versions of an AV product available today. It's also the most user-friendly tested here.
As the product installs, there are several introductory screens you can flick through, detailing such delights as Safesearch Plus, Phantom VPN, Software Updater, the Avira Password manger, and System Speedup.
There's also a useful tour of the interface, showing you what's what. But is everything in the product tour really included? Surprisingly, the answer is overwhelmingly yes. Most useful modules are all fully, or almost fully, functional.
The Software Updater fetches the latest version of your apps at the click of a button, the System Speedup cleans junk, but optimising startup performance is limited to the pro version.
The Privacy Pal module is fully functional, and cleans the digital traces that leave you open to being tracked across the internet. Similarly, the Password Manager, Safesearch Plus, and Browser Safety modules can all be installed in either Google's Chrome of Mozilla's Firefox browsers.
Even the Phantom VPN works, giving you 500MB of secure data transfer for when you're on the move in dodgy places.
File scans can be scheduled, and by default there’s a quick scan set to repeat every 168 hours or, as it's better known, weekly.
Overall, this is a very well specified free AV product that can give paid products a run for their money.
Get Avira free here.
Bitdefender Antivirus Free Edition
Bitdefender's free offering is simple, robust and reliable. Its paid-for version is our number-one recommendation right now, too.
By simple, we really do mean simple. There are no modules here that turn out to be paid versions, no password manager, and no secure browser to install. This is stripped back system protection only, offering just antivirus and nothing else. However, Bitdefender's AV engine employs the same machine learning as the full version, enabling it to spot unknown threats as well as known ones.
The interface is similarly sparse. You can drag-and-drop files on to it to scan them, but you can also right-click them in Explorer and do the same thing without dragging. Any dodgy files are quarantined, and you can also set up exclusions - both files and folders - that will not be scanned. This is useful if Bitdefender should produce a false positive that keeps preventing an application from running.
Overall, being stripped back to just the essential antivirus function, Bitdefender Antivirus Free Edition is very simple to use, with good AI-based protection. But if you need more, you'll need to look elsewhere.
Avast Free Antivirus
Unlike some some AV companies, Avast doesn’t hide its free antivirus offering so you can’t find it. A big orange button makes this version more obvious than its paid offerings, so that's a good start.
You must be careful not to opt in to Avast's data collection during installation as this will harvest a surprising amount of data, as revealed in this Vice article.
As well as basic protection, Avast Free Antivirus offers defence from unknown threats using its Behaviour Shield, which stops even previously well-behaved software from suddenly performing dodgy operations that could endanger your identity and data.
There's also a handy password manager, so you can log into sites in your browser by remembering just one password. This is pre-stuffed at installation time with login details found in your installed browsers.
What's not so great is that the system Cleanup Premier tool is an advert for the paid version. It will tell you what's slowing and bulking your computer, but you'll need to “buy” a free 60-day free trial. Similarly, installing the VPN and enabling it opens an invitation to subscribe to the service for a monthly fee.
Kaspersky is another big name in antivirus, and it offers a free version for PC.
While installing this product, you're implored to “Feel the power of protection” by the splashscreen, but it's no surprise that the free version doesn't come fully-featured.
There's no parental control, online payment protection, or VPN functionality here. But you will get all of the essentials, including file, email and web antivirus, automatic updates, self-defence, quarantine and more.
What's particularly good to see included is extensive right-click functionality against individual files. You can scan a file, send it to the Kaspersky Security Network to instantly have its reputation checked out.
You also have access to Kaspersky's cloud-based Application Advisor, which provides a full rundown about the content of the file, the number of users that have tested it, where in the world people are using it, along with various pieces of technical information.
As with Bitdefender's free offering, Kaspersky Free is a lightweight, solid choice.
Get Kaspersky Free here.
AVG Free Antivirus
Immediately after installation, AVG Antivirus Free offers to protect your phone, which is a clever move. Simply send the link to your device and download a free trial for the protection.
The other tools in AVG's arsenal must also be purchased, including the VPN, password manager, software updater, and AntiTrack module, which deletes tracking cookies. Most of these tools are included free with Avira's free offering.
AVG Antivirus Free offers six different scan types, including Deep Scan, USB/DVD scan, single file or folder scans, and a boot-time scan, which runs before Windows starts up, thereby running before any lurking malware has a chance to start up and protect itself from the product. If you're ever presented with a family member's computer displaying weird behaviour, this is the product to give that machine a thorough delousing.
In addition to AV duties, AVG also warns you of unsafe web links, and can block unsafe email attachments. Rounding out the product is a handy file shredder, right-click scanning for individual files, and a Do Not Disturb mode, which allows you to play games or watch shows without nag screens or other notifications.
In summary, this is a great product for deep cleaning your machines, but other offerings have more toys.
Get AVG free here.
Microsoft Windows Defender
Many people think Windows Defender is a joke. Built into Windows 8 onwards, it runs by default when no third party antivirus software product is installed. It's just a sop to appease windows haters, right?
Wrong. AV-Test has found that it detects and protects against almost all attacks, and scored it well for performance.
Being the default, there's a common perception that Windows Defender has no toys in the box beyond basic antivirus duties. This is not the case. For starters, there's ransomware protection that allows you to nominate folders that cannot be changed other than with your explicit say so. Integrated OneDrive support allows you to recover files that do become corrupted by malware.
Suspect samples can automatically be submitted for thorough cloud-based analysis. Being tightly integrated with Windows also allows Defender to provide innovative sign-in options, including Windows Hello, which allows you to log in with your face or fingerprint.
There's also the integrated Windows firewall, advanced exploit protection, and protection from code being injected by malware into innocent processes.
Secure Boot prevents rootkits or anything else from running and hiding before other software, including AV software, gets a chance to start up. Scanning duties include an offline scan that runs at boot time, before Windows starts, thereby denying rootkits and other stealthy malware a place to hide.
Finally, there are family options to help keep your kids safe online. Coupled with this, Windows itself has a little-used VPN built into the operating system.
There are more accessible free and paid-for choices, but if you really don't trust third party AV companies to keep your details safe, you could do much worse than Windows Defender.