Antivirus software is one of the things you should install on a new PC, and top quality protection can be yours completely free. We've updated our roundup of the best free security software so you know you're getting the very best protection for your data and your personal information.

It's fair to suggest that Windows 10's built-in antivirus solution, Windows Defender, is the last free AV you should trust to keep your system clean. Not that it's overtly bad – although it does tail behind just every third-party antivirus solution – but because it has a big target painted on it for attackers.

Windows users who haven't installed something hardier are the perfect hosts for viruses; attack the weak links, attack through the chinks in the one piece of software armour these weak links have by default, and you're in.

That's why we've dropped Defender from our list of free antivirus apps in this latest update of our free AV roundup. You need more than it can offer. If you're not running advanced virus detection, zero-day virus protection, anti-malware, anti-ransomware and other security essentials, you're not doing it right and leave yourself open to infections and identity theft.

Once again we've consulted the experts at the AV-TEST virus lab to find the most effective virus protection, and we've listened to your comments regarding usability, too. Free antivirus without popups, or at least some sort of seedy side, is a bit of a pipe dream – free AV is more of an advert than an altruistic gift. But we understand that for many of you the constant hassle presented by free AV popups can be a bit much to take – so if you're willing to sacrifice a minuscule amount of antivirus protection in favour of a cleaner experience, we're with you.

Want something stronger? Then check out the best paid-for antivirus software

Divider

1. Avira Free Antivirus

Bitdefender Antivirus Free edition has received a major overhaul and taken the top spot in our free antivirus roundup. It’s the best free security software you can download today
1. Bitdefender Antivirus Free Edition

Given a new lease of life, with fast virus-busting and a clean interface

As if, in our previous roundup, the folks at Bitdefender heard us moaning about the fact that its free product hadn't had its engine updated since 2013, along comes a brand new version at last.

Essentially consisting of the AV section of the full product, Bitdefender Antivirus Free Edition's clean, light, well constructed scanning mechanisms – which are almost universally faster than the industry average – and unrivalled virus definitions mean it's pushing back towards the top of the tree. AV-TEST's December testing round did pick out a few flaws in its handling of zero-day threats, however.

The free version's insistence on running in autopilot mode is a double-edged sword, making the process of virus management easy but taking it out of the user's hands; while we're inclined to trust it, there have been cases in the past of automatic systems going slightly rogue, such as the incident a few years back when Panda Antivirus identified itself as a virus and locked up a large number of Windows systems.

While Bitdefender isn't exactly popup-free – it can be quite annoying, in fact –it's clean, clever, and efficient enough to take our top spot this time.

Review and where to download: Bitdefender Antivirus Free Edition

Divider

2. AVG AntiVirus Free

Following its takeover of AVG, Avast now benefits from a much larger userbase, all reporting details of new security threats
2. Avast Free Antivirus

A much-improved free antivirus suite, bolstered by a new, expanded userbase

Avast and AVG haven't yet fully merged, despite the former formally acquiring the latter in mid-2016. The newly combined company says the two free antivirus products will remain separate, although there's apparently a joint AV package on the way soon. Obviously, though, Avast now has a lot more data to work with, having expanded its effective userbase (and, therefore, its threat detection network) to a whopping 400 million users.

The latest edition of Avast Free Antivirus adds an automatic gaming mode to mute popups and reduce system load when you're firing up a processor-hungry game, which is very handy indeed, and the interface has been given a clean new overhaul. There's a password manager, too, which is an undeniably good addition to your security portfolio.

It scores well on AV-TEST's widespread malware benchmark and continues a clean sweep against 0-day attacks – presumably that expanded detection network is really helping. Less impressive is the slight negative effect Avast has on software launch times, and its slightly popup-heavy attitude.

Review and where to download: Avast Free Antivirus

Divider

3. Panda Free Antivirus 2016

Sophos Home delivers enterprise-level antivirus protection for home users
3. Sophos Home

A recent entry on our list – but the perfect choice for a home full of PCs

Marketing itself as “business-grade security”, Sophos Home does a little more than most free antivirus software, and actually seems better suited to families.

You get standard antivirus and anti-malware protection, along with browser tools like anti-phishing and, most importantly, content control. Combined with central management of up to 10 PCs, this means you can effectively lock down your kids' browsing options.

Although AV-TEST hasn't formally assessed Sophos' skills, fellow lab AV-Comparatives offers a decent rating of its antivirus abilities. Desktop notifications can be a bit intrusive, though since Sophos Home isn't a direct advert for another comsumer-level product (the company mainly deals with business software) you're not constantly badgered with requests to upgrade.

Review and where to download: Sophos Home

Divider

3. Panda Free Antivirus 2016

Kaspersky has finally launched a free version of its extremely successful antivirus software
4. Kaspersky Free

It's finally here! Kaspersky's first foray into free internet security

The paid-for version of Kaspersky's Windows security software frequently tops charts of best antivirus solutions and AV-TEST once again gave it full marks across the board in its latest round of testing.

As you would expect, Kaspersky Free is a scaled down version of the full program, ditching additional features such as privacy protection and safe payment sandboxes to concentrate on powerful, no-frills and – most importantly – free protection for your PC. The result is a tremendously easy to use and navigate bit of software that does an effective job of keeping you protected from viruses.

Using the nuts and bolts real-world scanning engine of the paid-for suite, Kaspersky Free is fiendishly hard for viruses and trojan horses to break down. And we love that it doesn't constantly pester you with nudges to upgrade to the full version.

Review and where to download: Kaspersky Free

Divider

4. Comodo Free Antivirus

Avira Free Antivirus remains a superb free antivirus suite, but its frequent popup alerts are annoying, resulting in a drop down our chart
5. Avira Free Antivirus

Great antivirus, but a little noisy for our liking

Avira Free Antivirus for Windows continues to score highly on AV-TEST's stringent testing program, quashing 99.7% of tested threats, and it generally doesn't put too big a burden on your hardware.

It has a clean, friendly interface – with a swish redesign ready for 2018 – and throws up minimal false positives. The introduction of a free security suite to optionally run alongside it – with ransomware and phishing protection, a 500MB/month VPN and various speedup promises – just sweetens the deal. This is one of the best free antivirus packages of 2017.

So why, then, have we dropped it from the top spot on our list, a position it's held for the past two years? It's the constant badgering. There's a certain level of popups and advertisements that's acceptable for a free product, and Avira has begun to cross the line. It's not as onerous as some –Comodo's over-enthusiastic interface comes to mind – but booting up your PC to see Avira shouting at you once again is jarring.

Review and where to download: Avira Free Antivirus

Divider

5. Avast Free Antivirus

AVG now benefits from Avast’s added antivirus expertise, but isn’t as strong as its parent company’s free software
6. AVG AntiVirus Free

Free, nice looking antivirus, but lacking in a couple of areas

There's a growing trend amongst some online pundits to label antivirus apps like AVG – and, indeed, AVG specifically – as 'crapware'. We don't subscribe to that definition; if that term is supposed to mean that these apps are ineffective or pointless, it's simply not true.

AVG offers (reasonably) effective virus protection for free, and it does so with minimal system impact. If, on the other hand, the derogatory term refers to products which go a little heavy on the advertising and features that don't matter – AVG AntiVirus Free's 'tune up' portion, for instance – perhaps the shoe fits here.

Popups or not, it's the antivirus we're most interested in. Looking at AV-TEST's figures, and considering AVG shares the same expanded userbase as Avast, we were a little surprised that its strength doesn't quite match up to its new parent, and anti-phishing tools could use some improvement, too. Speculatively, this could mean AVG's engine is not getting the same love it once did, or that Avast's is slightly stronger – whatever the case, keep your eyes open for the combined Avast/AVG antivirus that's on the roadmap for this year, because both products running in tandem will be just about unbeatable.

Review and where to download: AVG AntiVirus Free

Divider

6. ZoneAlarm Free Antivirus + Firewall

Despite its use of remote cloud servers, Panda Free Antivirus still puts considerable pressure on your PC’s resources
7. Panda Free Antivirus

Feature-rich PC security, but not as lightweight as it promises

The eternal battle against popups doesn't exactly start well, with Panda's site throwing a huge banner up shouting about a discount on the full version before you're even allowed to download the free one.

Put that aside, however, to look at the software itself: Panda's entirely cloud-based antivirus solution goes about as lightly on system resources as is possible, at least when it's quietly running in the background. But you'll probably find, as AV-TEST's lab did, that Panda Free Antivirus has a bigger impact on many common system tasks – installation, copying files, downloading apps – than most of the opposing AV apps. We also experienced heavy CPU peaks both at random times and when Panda was updating itself.

That said, Panda's overall look –which offers calming vistas where other go for plain white or grey – is refreshing, it's incredibly well laid out, and it comes bundled with a bunch of extra features that don't just seem like fluff. It dials itself down even further with a game mode when you need extra CPU speed, offers to immunise USB sticks (handy if you're worried about preinstalled spyware), has a bootable rescue kit in case a malicious program cripples your Windows install, and includes a threat-weighted process monitor.

Review and where to download: Panda Free Antivirus

Divider

7. Immunet AntiVirus

It might be an effective antivirus suite, but 360 Total Security gathers a considerable amount of data about your activity and reports it back to developer Qihoo
8. 360 Total Security

Antivirus overloaded with features, with a potential sting in the tail

The specter of developer Qihoo's VW-esque cheating of AV tests seems to be lifting a little these days, and it's hard not to recommend it when you consider exactly what it's offering up for free: AV protection from several concurrent engines (Bitdefender, Avira, and Qihoo's own engines) along with reasonable extras like anti-phishing and a mobile app to help manage multiple systems.

360 Total Security Free Security doesn't bombard you with popups, which many users will love, but we do have serious concerns about its privacy policy, particularly considering that signing up to Qihoo's data-collecting User Experience Improvement program is set as default. The company has no qualms about collecting sensitive information about you, and what it does with it at the other end is anyone's guess.

We're also not hugely impressed by its interface. You'll need to do some fiddling to get several antivirus engines running at once, and doing so with the rather messy UI is not easy. A lot of the bundled tools seem extraneous, and we a couple of false positives in testing too. So if you want quiet, strong protection this is a fine option – but you'll need to do some work, and you may have to pay a high price.

Review and where to download: 360 Total Security

Divider

8. Qihoo 360 Total Security Essentials

As the name suggests, ZoneAlarm’s real expertise lies in its firewall technology
9. ZoneAlarm Free Antivirus

Licensed antivirus and noisy alerts, tacked on to a solid firewall

ZoneAlarm's reputation in the firewall world precedes it, and while that particular aspect of this all-in-one package isn't what we're really concerned with here, it's a solid extra if you don't trust your router or Windows' built-in firewall.

The antivirus engine on offer here is actually licensed from Kaspersky, so although we were unable to find any results from independent testing labs – hence its position this low on our list – it's safe to have at least a small amount of confidence in its abilities. It's well laid out, easy to use, and is your only real option if you want to use the ZoneAlarm firewall alongside any anti-malware app other than Windows Defender.

That said, ZoneAlarm Free Antivirus + Firewall isn't a quiet program, alerting you of every little thing that's been blocked or deflected – some people like that, others will quickly become infuriated.

Review and where to download: ZoneAlarm Free Antivirus

Divider

9. Bitdefender Antivirus Free Edition

The newly rebranded Adaware Antivirus Free offers fewer features than its last iteration
10. Adaware Antivirus Free

Rebranded but cut down, with a large amount of advertising on board

A new name for what was once Ad-Aware Free Antivirus+, to celebrate its company's rebranding from LavaSoft to Adaware.

As another antivirus package with a licensed engine – this time from Bitdefender – and the benefit of Adaware's history in anti-spyware, you'd expect its results to be good. But things aren't so rosy.

This new Adaware Antivirus Free 12 drops the Companion from version 11, which blocked malicious and fraudulent URLs; it now acts only on iffy . There are a host of other promised features, but they're not actually there – placed, tantalisingly, on an interface which very much shouts 'adware' more than it does 'adaware'.Better to go for one of the other on this list rather than be dazzled by its slick, shiny interface.

Review and where to download: Adaware Antivirus Free

Divider

10. Windows Defender

Comodo Free Antivirus offers handy sandboxing, but its malware protection leaves much to be desired
11. Comodo Free Antivirus

Free AV that needs a little work before it's ready for widespread use

Credit to Comodo for updating the look of Comodo Free Antivirus for version 10 (although older appearance options are still there if you look for them), and for its strong showing against AV-TEST's zero-day threat assault.

Bad news, though on just about every other front: Comodo Free Antivirus flunked the widespread malware test, coming way below the industry average – far, in fact, behind Windows Defender –and it's rather heavy on the system, too.

If you're worried about popups and ads, you're also in a bad place. Some of Comodo's tricks are pretty insidious. If you manage to install it without a host of Yahoo branding making its way onto your PC, good for you. Then there are the 'Geekbuddy' popups to deal with – a paid-for consultation service, though that's not made clear. We completely understand the need to make something back from free products, but we'd rather the assault weren't quite so violent.

There are positives, though: its ability to sandbox off your browsers is handy, but not enough that we'd recommend an install.

Review and where to download: Comodo Free Antivirus