Best Free Antivirus Software


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Antivirus software provides an essential layer of protection from viruses, trojans, worms, spyware, adware, dialers, keyloggers, and rootkits. However, don't let the name antivirus confuse you. These days every good antivirus has good detection rates for all forms of malware, not just viruses. The term malware includes viruses, trojans, worms, spyware, adware, dialers, keyloggers, rootkits, and any other software which performs malicious activities on a computer.


Sadly, the amount of malware currently in circulation is so large that no antivirus could possibly detect all of it. Despite vendor's claims, no single antivirus solution can detect nearly all new malware. There are some products out there, including some in this review, which include technologies which are able to adequately protect a computer, but any product which relies mainly on detection is statistically doomed to fail eventually. Also, using more than one real-time antivirus at the same time uses much more system resources, can cause system errors, and can even reduce protection due to unintended conflicts. For my advice on how to compensate for these weakness of antivirus products please see my other article about How to Stay Safe While Online. Having a good antivirus product does go a large way towards adequately protecting your computer, but in this day I would highly recommend that you add additional layers to your security arsenal.


Below I have reviewed some of the most effective Free Antivirus products currently on the market. In order to make this review more unbiased, although I do of course admit that my own intuition and experience does affect my judgment as well, I came up with a particular methodology for comparing these products. This methodology is described in the following section.

Recent Changelog:

18-12-2015 - New article editor: Added products to be reviewed

Products to be Reviewed:
  • Avast Free Antivirus
  • Avira Free Antivirus
  • AVG Antivirus Free
  • Baidu Antivirus
  • Bitdefender Antivirus Free
  • Clearsight Antivirus
  • Comodo Internet Security Premium
  • Fortinet FortiClient
  • Nano Antivirus 
  • Panda Free Antivirus
  • Qihoo 360 Total Security
  • Roboscan Internet Security Free
  • Sophos Home Antivirus
  • Windows Defender
  • ZoneAlarm Free Antivirus + Firewall


Methodology For Comparing Products

The main motivation behind why I came up with this particular methodology for this review is that I value system protection against real world threats above all other categories by which an antivirus is commonly judged. It does not matter to me whether an antivirus protects the user by detecting malware, blocking dangerous sites, behavioral analysis, sandboxing, or any other approach. The most important thing is that at the end of the day your system is safe from infection. Thus, that is the attitude I have taken towards reviewing these products. My criteria is entirely based on protection, not cleaning. Therefore, if you believe your computer may be infected please first see my article on How to Know If Your Computer Is Infected before continuing to read the rest of this article.


I have located reputable Antivirus testing organizations which claim to test products against situations which resemble real-world situations. I narrowed these down by further requiring that the organizations have a relatively long record of producing good, seemingly unbiased, results. The organizations I ended up with, and therefore used for this review, are:



Dennis Technology Labs

From here I looked at all tests spanning back over the last two years. However, if there were more than three tests within that range I used only the most recent three. Also, if given the choice between results from different operating systems, I chose that for the most popular operating system. At the moment Windows 7 is the most popular operating system.

Also, I only considered results if it was specifically the Free Version which was tested. This is because the results for the Paid Version of the products in this review, with the exception of Comodo Antivirus (which has the exact same protection for its Free and Paid versions), are often quite different from those for the Free versions. Many marketing teams try to cloud this difference, but for the purposes of getting the most reliable information I am strict about this. Unless it can be explicitly proven that every protection mechanism is exactly identical to the free version the results for paid products are not considered in this analysis.

In addition, I did not count it against any of the products if they were not tested by multiple organizations. As long as they were tested by at least one, within the above-mentioned period, they were considered. This criteria was chosen because there are many reasons to choose not to participate in a test. Thus, it should not be held against the product if they were not tested by multiple agencies. However, if they were not tested by any, this makes it impossible to compare them in an unbiased fashion.


Once this data was collected, I then looked at the overall results for the Free Antivirus products discussed in this review, and ordered them mainly according to the quantitative results. However, my own knowledge of the products, and the reviews and experiences of others, were also considered. The results are presented and discussed below.

Discussion And Comparison

Comodo Antivirus is my top pick for advanced users, or for Intermediate users who are okay with an antivirus software which will occasionally ask them for input. However, if you do not fall into those categories, or for any other reason find it to not be a good fit for you, then you will likely find my next pick suitable. Also, for those who prefer a complete solution, there is always Comodo Internet Security (CIS), which is also free and includes a firewall in addition to all other components which already come with Comodo Antivirus.

Firstly, I will note that I am a volunteer moderator (not employee) on the Comodo forums. However, this is certainly not the reason I chose this for the number one position. The reason I made this my top pick for advanced users or users who are okay with a somewhat talkative antivirus software, is because it is the only product which I feel confident saying that it will protect you against nearly 100% of real-world threats. This is because it maintains a white-list of known safe applications. Then, all unknown applications, which include all unrecognized malware, will be sandboxed and isolated from the rest of the system. Thus, this product provides very strong protection against even zero-day malware.

Comodo Antivirus also uses the cloud to facilitate the detection of the most recent malware, as do many other Free Antiviruses reviewed in this article. It will also analyze unknown applications for suspicious behavior, and alert the user accordingly. However, as mentioned previously, users who do not want a somewhat talkative antivirus should continue to my next pick. Also, by default Comodo Antivirus has small advertisements (which can be disabled as shown here). Also, please see my notes in the Quick Selection guide for advice on how to avoid unwanted software during installation.


Panda Cloud AntivirusPanda Cloud Antivirus is an excellent choice for average users, who may find Comodo Antivirus too confusing. It has a simple interface, completely automated features, access to cloud-based protection, and has been shown to be very good at protecting a computer. Panda Cloud Antivirus has a behavioral blocker, web protection, and access to cloud-based protection, all of which will help increase your security. The protection offered by this product is very strong. However, do note that it will auto-quarantine files which it believes to be dangerous.




Avast! Free AntivirusAvast! Free Antivirus has very good protection rates. Avast has many different protection shields, boot-time scanning, a behavioral blocker, an internet site ratings plugin, script malware protection, and access to cloud-based protection. It's arguable whether their ratings plugin offers comparable levels to Web of Trust, but the script malware protection can prevent certain browser exploits, a feature not available in any of the other free AV's reviewed.

However, do note that Avast requires a free registration to function after 30 days, and the default installation installs the Chrome browser unless you uncheck it. Also, note that the OpenCandy advertising component is integrated into the Software Updater tool in Avast. More information about OpenCandy can be read here. Thus, if a user selects this option during the install they will end up with OpenCandy on their computer. My advice would be that if you want to install Avast you should not use the Software Updater tool.


AVG Anti-Virus Free EditionAVG Anti-Virus Free Edition is also a good choice for average users. My analysis of the results, as discussed in the methodology section, does show that it does a decent job of protecting your computer. However, it appears that the above Antivirus products tend to do better. Also, it comes with advertisements (but they can be disabled).





360 Total Security is also a good choice for average users. Although it has gotten some very stellar reviews, the results I found from looking at the results from the testing agencies referenced earlier in this article show that the protection it provides is roughly the same as AVG, but certainly not as effective as Comodo, Panda, or Avast. This product uses multiple antivirus engines to detect malware. It has cloud protection, and also uses the Avira and BitDefender engines, although these are not enabled by default. For more information about this antivirus, see the separate article on this page.

Avira AntiVir Personal EditionAvira AntiVir Personal Edition is another product which has a very good reputation. However, the free version was not tested by any of the three testing organizations I referenced in my methodology. Therefore, I cannot currently recommend it above any of the previously mentioned products.

However, other comparative tests do show that it has very high detection rates for malware. Also, many users have used it and found that it is very effective. Also, Avira provides access to cloud-based protection. AntiVir is certainly a good choice for a free antivirus, but due to the lack of real-world testing, at this time I cannot recommend it above the other products in this review. Hopefully in the future they will have the free version tested by these organizations as well.



Bitdefender Antivirus Free Edition

Bitdefender Antivirus Free Edition is another free antivirus product which has a very good reputation. However, the free version was not tested by any of the three testing organizations I referenced in my methodology. Therefore, I cannot recommend it above any of the previously mentioned products.

The engine for this product appears to be very similar the commercial product, although there are some tweaks. However, the level of protection provided has not been shown conclusively to be identical with the paid version, which is why I did not use the results for the paid version in my analysis. Bitdefender Free has both local and cloud-based definitions. Thus, users always have access to the most up-to-date definitions. It also has an effective heuristics engine, and uses a component called the Active Virus Control to monitor applications in real-time for suspicious behaviors. In addition it also has a webshield, which seems quite effective at protecting users from both malware infested and phishing sites.

The user interface for this product is very minimalist. Thus, it may be attractive for novice users, although more advanced users may be frustrated at the lack of customization. However, it has no offline installer, and it also requires registration to continue using it past 30 days. Bitdefender Antivirus Free Edition is a good choice for a free antivirus, but due to the lack of real-world testing, at this time I cannot recommend it above the other products in this review. Hopefully in the future they will have the free version tested by these organizations as well. Also, note that if you are having trouble getting Bitdefender Antivirus Free Edition to install in English please follow the steps in this post.


Please help us by rating this review

End-Note: Please note that I also looked into Forticlient , Kingsoft, and Microsoft Security Essentials. However, I found that the protection offered by these products is subpar. Thus, if you are considering using Forticlient or Kingsoft I would strongly recommend that you instead consider another of the products reviewed in this article.

Related Products and Links

Other Articles By Chiron

Related Free Antivirus Software Articles

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Quick Selection Guide

Comodo Antivirus

Gizmo's Freeware award as the best product in its class!

Runs as a stand-alone program on a user's computer
This has full real-time protection capability, including real-time antivirus, behavioral blocking features, cloud-based protection, and an automatic sandboxing function which protects users from nearly all malware.
The automatic sandboxing function, although not very intrusive, may be too talkative for some users. Also, by default non-intrusive advertising is enabled (although it can easily be turned off). Also, Comodo Secure DNS, which is offered with Comodo Antivirus during installation, tends to have many false positives. Thus, I would suggest that you untick the option to Enable Comodo Secure DNS during installation.
Version 6.x
32 and 64 bit versions available
Unrestricted freeware
There is no portable version of this product available.
Take care to avoid the installation of unwanted software during installation. To do this use the customized installer button, which is on the lower left-corner of the screen during installation. Additional software, including a browser, an ad-blocking addon, and an option paid service which would allow Comodo technicians to help you with computer problems, are all included by default. Also, I would suggest that you untick the option to Enable Comodo Secure DNS during installation. It tends to falsely block many safe pages. Also, note that although the download page linked to above does not list Windows XP as being supported, Windows XP x32 is fully supported, although Windows XP x64 has significant limitations.

Avast! Free Antivirus

Runs as a stand-alone program on a user's computer
This has full real-time capabilities, behavioral blocking features, script malware protection, and a low rate of false positives.
Default settings require certain user interaction. It is bundled with Chrome browser by default, and if not carefully avoided during installation the user may accidentally install OpenCandy (see discussion for clarification).
Version 9.x
32 bit but 64 bit compatible
Feature limited freeware
There is no portable version of this product available.
Take care to avoid the default inclusion of the Chrome browser and OpenCandy during the install process by using the custom install option. The attempt to install these will also be repeated at the program update if the automatic option is chosen. Quick Start Guide: Forum:
Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8.x, Mac OS

Panda Cloud Antivirus

Combines a web service with a stand-alone program
High detection rate of malware, web protection, some behavioural blocker features
Detection rates of real-world malware is slightly lower
Version 2.x
32 and 64 bit versions available
Free for private use only
There is no portable version of this product available.
Windows XP, Windows Vista, Windows 7, Windows 8.x

360 Total Security

Runs as a stand-alone program on a user's computer
Contains many engines for malware detection.
Avira and Bitdefender engines are not enabled by default.
32 bit but 64 bit compatible
Unrestricted freeware
There is no portable version of this product available.

AVG Anti-Virus Free

Runs as a stand-alone program on a user's computer
Behavioural blocker
Slightly lower signature detection rates
Version 2013.x
32 and 64 bit versions available
Free for private use only
There is no portable version of this product available.
Forum for support
Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8.x

Bitdefender Antivirus Free Edition

Runs as a stand-alone program on a user's computer
High detection rates, very user friendly
Lack of customization, no offline installer, requires registration after first 30 days
Version 1.x
32 bit but 64 bit compatible
Free for private or educational use only
There is no portable version of this product available.

Avira AntiVir Personal Edition

Runs as a stand-alone program on a user's computer
Outstanding detection of malware
Not the most user friendly
Version 14.x
32 bit but 64 bit compatible
Free for private use only
There is no portable version of this product available.
Windows 2000, Windows XP, Windows Vista, Windows 7, Windows 8.x

This software category is maintained by volunteer editor George.J. Registered members can contact the editor with any comments or questions they might have by clicking here.


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Average: 4.3 (2084 votes)


Please let people know that BitDefender is no longer compatible with Windows7.


This is not true. MC - Site Manager. "Operating system: Windows XP SP3 32-bit, Windows Vista (SP2), Microsoft Windows 7 (SP1), Microsoft Windows 8. RAM: 512MB. Hard disk space: 700 MB".

Reluctantly I've just abandoned Comodo AV after yet another nightmare install attempt (in fact, many attempts!). Version 7 worked fine but version 8 wont install despite following Chiron's clean install guide on the Comodo forums to the letter - Comodo keeps on saying it can't load because Avast is incompatible despite me looking everywhere and, as far as I know, removing everything to do with Avast. I also used the firewall part of CIS and I particularly liked the way you could bind applications with Comodo, for instance, to a VPN to safeguard against disconnects.

Anyway I've switched to Panda free AV and working nicely - never used it before and wasn't aware of its excellent performance in recent AV tests.

It is important to understand this is not Comodo's fault, but that of Avast! and I have encountered similar "after Avast!" issues with other security programs, especially when the Avast! uninstall tool provided by the vendor has not been used. MC - Site Manager.

Yes, I completely agree. The problem is very much with Avast, and having used both their removal tools and searched manually for any remnants, I and the avast community have run out of ideas.

PS - I hope it didn't seem as if I was blaming Chiron or the excellent work he does both here and on the Comodo forums.

One of the things I love about this site is that the reviews are always reviewed, meaning that when things change, you often update the best-of lists. And the comments are often very helpful.

Just out of curiosity, though, wasn't Microsoft Security Essentials top rated a while back? O_O But now it's off the list and just mentioned as sub-par? OHMY! What happened?

Also, an update of Avast gave be blue screens of death, and when I uninstalled it and tried to go to Comodo, it said I already had it and couldn't upgrade directly. I'm thinking it's because I have the firewall version. I reinstalled Avast but chose the minimal bells and whistles. So far - so good, but I'm thinking of uninstalling the Comodo firewall and trying Comodo anti-virus again.

Anyway, again what happened to MS Essentials?

I have been using Panda Cloud free for a few weeks and am generally pleased. However, it can use a lot of memory at times...Just my system or have others here experienced this?

http [ COLON ]//avlab [ DOT ] pl/sites/default/files/files/performance_test_november_2014.pdf Performance Test at AVLabs - November 2014 Probably the most complete performance test for antivirus suites I've seen around the web. It compares the performance of both free and paid solutions [and all of them].
Very interesting. It is useful to see idle resource loading but the performance testing is limited to trivial activities. It would have been nice to see performance statistics while performing less trivial functions including web browsing, downloading, and quarantining/removing actual threats.

I tried 360 for the first time this week, and I'm really liking it.

Unusually for a "suite" I'm actually finding all of the different modules useful as well.

It took me a little while to realise that activating the Avira and Bitdefender modules seems to be a two-step process. I ticked boxes that I thought had activated them and only later found other activation switches in the actual scan dialogue.

It is a little bit buggy I think ... some of the pop-up notices appear a bit erratic as to whether they decide to show themselves or not and it also seems to fall prey to the common W7 issue of disappearing systray icons. Installing it into a clean W7 seems to have helped with that though for now.

Some of it is a little confusing to a first-time user ... for instance I ran the Cleanup module which broke ClassicShell for me, until I realised that it had quarantined the toolbar components of ClassicShell.

All in all I like it a lot though, especially the alternative Windows updater. It seems to run happily with Comodo Firewall too and performance is still good even on my elderly 2Ghz/2Gb desktop machine.

By the way Chiron, your Dennis Technology link goes to the 2013 test results.

Thanks for a great article anyway. I've been using Comodo CIS for a couple of years or so now but I was finding that the AV component was a bit demanding on my low-end hardware, so this week I've tried out most of the alternatives on this page.

Panda I liked quite a lot ... I've used their portable on-demand scanner for a while now so I thought their free AV would probably be pretty good. Which it is, although for me it lacked some configurability and I didn't really like the auto-quarantine behaviour either. I tried 360 just out of interest really but I think I'll stick with it for a while. I seem to recall some concern about their privacy practises a while back but I've not heard that mentioned since.

I noticed this week that none of these AVs seem to flag the Nirsoft suite as malware ... I don't know if this is due to Nirsoft finally getting the message through, or some other factor such as heuristic scanning.

I'll still be using Emsisoft and MBAM as on-demand scanners as these two between them seem to pick up everything.

I see by the by the way that Comodo has received its first update in some time. I really happy to find that the awful process of unblocking blocked executables and adding them to the trusted list has been changed and is much easier now. But again, a bit erratic ... some blocked files can now be trusted via a small screen pop-up, while others still require the tedious process of opening the main program and adding to trusted, etc etc. I noticed also that some execs continue to run even though they get added to the "unknown" list and I have everything set to "block".

I see the settings dialogue has changed too though, so maybe there's something there which might explain that.

Thank you for your detailed response. It was very helpful. I've updated the link for Dennis Technology Labs. I also added a note about the auto-quarantine in Panda. As for Comodo Firewall, in case you weren't aware, a new version has been released to the Comodo forums. It can be downloaded from here: Please let me know if you have any questions, or if you find out anything else. Thanks.

Just a quick update ... the issue I mentioned whereby some processes triggered a "do not block again" dialogue while others have to be added to the list manually.

It seeme that this is related to system resources, so that when the machine is working hard the dialogue will take a long long time to appear.

Chiron, I installed Comodo Antivirus on my laptop with Windows 7. I plugged in a pen drive containing my software collection. Comodo detected some files as suspicious. I chose the option to ignore and add to exclusions, but this does not seem to work. Even choosing ignore once did not seem to work. It just kept on popping until I chose the option to either quarantine the file, or report it as false positive. How do I solve this problem? It's quite annoying.
Sadly, this sounds like a bug to me. I do know that ignore once does not work correctly (even though it was reported long ago by me). However, I was not aware that exclusions does not work correctly for removable drives (which is what this sounds like). If you are able, it would be very helpful if you could make a bug report for this on the Comodo forums. However, as a workaround, I would say that if reporting it as a false positive allowed it to work correctly, perhaps that is the best option for the time being. Thank you.
I too had the same thought, that this might be a bug related to the file being on a flash drive. I don't think I will be posting about it on the Comodo forum, as I do not intend to use the software for long. Strange that not anyone else has found out about this bug yet.

Most of antivirus programs have this problem (well, I know for Bitdefender and I think Symantec also). My workaround is to temp. disable on access protection.

Exclusion would not be very smart option with removable drive, IMO.

I am using [edited] for antivirus. Is that a good version, or does it have weaknesses? What other malware product would work good with it. I use Windows 8.1 platform.

Please do not post about commercial antivirus here. This is a freeware site, and we allow discussion of only free software. If you have queries about any of the free software, you are welcome to post. But, if you want to post about commercial software, you will have to look elsewhere on the internet.

Personally I don't use any AV on all of my machines recently and I feel pretty comfortable! No single issue for a very long period of time. As I have said many times - the use of AV software is too much overrated nowadays, especially if you are an experienced user. Moreover (just like with the cars) - I'm a big fan of performance, not of the security. There's not such a thing like "AV light on resources" - they all have impact on your system, always!...

Cheers everybody! :-D

There are some AV light on resources; I'm using Panda free Antivirus and I'm impressed by its very low usage of RAM and CPU. In this moment this is the RAM used by Panda on my PC:
PSUAmain.exe: < 1Mb
PSUAservice.exe: < 1Mb
PSANHost.exe: 11 Mb
AgentSvc.exe: 9 Mb

It actually depends on your system resources. If you're having enough resources, you won't find any lag. Moreover I believe what you posted here is the idle RAM usage. Try starting a scan, or opening documents, installing executables, copying files, browsing internet, CPU usage etc that can also include in resource consumption.

The real performance of your system often doesn't depend only from some numbers which you can see in Task Manager. That's a general deception...

Personally, although a small subset of users may not feel that an antivirus is suitable for them, I do believe that an antivirus still has a significant role to play in terms of protecting a computer. For a more in-depth explanation of what I believe, and why, please see this section: of my article about How to Stay Safe Online. Thanks.
While you as an experienced user may not need an antivirus, general users still need one. Security is important for them.

I tried the latest version of Avast! (Avast 2015), and didn't like it: it is heavy and cluttered with useless stuff, it's an antivirus that tries to be cool and fashionable with social features, badges, prizes, karma and Facebook, which is not what I need from an antivirus.
At some point my computer was almost stuck: one of the Avast files was using 200+ MB of RAM and growing, and it was using at least 20% of the CPU resoruces, not sure for what reason, because couldn't tell from the user interface and it was unclear how to stop whatever it was doing. It's the kind of situation that makes me remove a software right away, because I don't like when a software does not show clearly what it is doing and ruins the performance of a computer.
Currently I removed Avast and I'm trying Panda (v. 15.0.3).

I have to agree, the new Avast! looks great and all but it just became the new AVG but its resource usage is better than AVG

The process that was causing that usage was probably the new Avast! NG. You can read about it here,

Its sounds good but it takes up to 2GB of my HDD space, I'm also currently trying Panda

The download link for "Panda Cloud Antivirus" is outdated, it's not working. I got it through the official website.

Thank you for pointing this out to me. The link should now be fixed.

If I may put my two cents in, Bitdefender free edition is not a good choice.

You have to download an installer -an offline intaller simply does no exist- and the installation needs several consecutive downloads even after the installation. The first definitions update takes a while and sometimes goes wrong, so the program forces you to start the updating process again. I know this because I tried installing bitdefender on different PCs from friends and relatives, so I can say the process isn't as smooth as you'd want.

The installer does not include an uninstaller, you have to download a third party one if you ever get bored (or annoyed) by Bitdefender. Also, you have 30 days to test the product, after that period you are forced you to create a free BitDefender account or login with facebook or G+ within the app to continue using the product.

IMHO, not the best of approaches.

Agreed with the points. For the same reason, I was not able to install this antivirus on an old computer which is not connected to the internet. I was looking for a lightweight antivirus, and I thought BDAV free would be a good choice. But, lack of offline installer, and creating a free account was what put me off. Even if offline registration was possible with it, like Avast has, I would have given it a try, after connecting the PC to internet for a while. But, given the present situation, gave it a miss. With lack of customization, and these issues, they are really making it hard on themselves for users to be able to accept this.