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.

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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

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

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.

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

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.

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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Thank you UserError and Anupam. I have now added information about the lack of an offline installer and the required registration to the article. Thanks again.
Thank you for letting me know of your experiences with this product. I will keep this in mind. Also, what are others experiences with this product. Have you run into as many problems with it as UserError? Thanks.
360TS now has it's own new website, totally for the product:
Wonder if this is the prelude to 360IS being discontinued? MC - Site Manager.
Version 5.2 beta is now released. I don't understand why they are trying to make the UI similar to that of Baidu's.
There appears to be some sort of agenda in play here. No doubt all will be revealed in time. Problem is the balance of opinion is still well in favor of IS over TS. MC - Site Manager.
That would make me sad :( Anyway it's still getting product updates, although minor ones. 360 Internet Security'D' has been released. Currently the IS version is more stable than the TS version.

I thought you should know that it has gone worse, now Comodo SecureDNS completely blocks access to Qihoo's English website:


It's worth noting that this didn't happen before, it was only blocking the download.

Thank you for keeping me up-to-date. I have been keeping an eye on it, and I believe the number of false positives it gives is too large. I have therefore updated my information for this article. I now recommend that users untick the option to Enable Comodo Secure DNS during installation. Thank you very much for bringing this to my attention.

it may not be a false positive. there are many corporations (one of which i worked for) that have proprietary secrets and/or negotiations ongoing for business deals. our servers were repeatedly hacked by hackers located in china. how they accessed our systems led to the banning of communist/state owned/chinese software for all employees in sensitive areas. i guess it make sense(?), i doubt the u.s. military used soviet cloud based antivirus software to secure their systems during the cold war, lol. perhaps comodo is aware of this building tension/caution within governmental and business environments.

File Detection Tests Real World Protection Tests Avast does extremely poor in File detection tests and came last. Excellent results for Avira (Pro) and Qihoo. Panda does a fair job.
As per my methodology I only use the results from Real World Protection Tests. In those Avast has consistently been doing quite well. The issue with File Detection Tests is that they really only test what has become just one part of the job of an antivirus. These days what matters is how all of the protection layers add together to protect a system. Thus, focusing on just one, such as File Detection, doesn't really give a good picture of the protection capabilities. That is why I leave out any descriptions of file detection statistics, even though historically that used to be what was most important in terms of protection. Let me know if you have any questions, or concerns, about this methodology. I am always looking for issues with it so that this advice can be improved. Thank you.
Thanks but Avast faired poorly in file detection mainly because of the 140 false positives!! :| Anyway these results change from time to time.
I have thought about including False Positive information, but still have to find some tests which I believe are decidedly real-world enough in terms of how likely users are to actually run across false positives of the type they are being tested against. I will look into including information like this in the next rewrite, assuming I can find some tests I am happy with. Thank you.

I tried to download Qihoo's 360 Total Security to test it but I got this warning message from Comodo SecureDNS:

Any idea what's this all about?

That is a false positive from Comodo SecureDNS. I have reported it to them as a false positive. Hopefully the detection will be removed in the next few days. If detection is not removed within 5 days please let me know. If it takes that long to remove a false detection I would rather advise people to not use the SecureDNS, but disable that particular feature. Thus, please keep me updated about this detection. Thank you.

Will do and you're welcomed.

I am still curious as to why "MSE" isn't included in that list? It remains to this day one of my favorites and from my experience it proved to be an excellent set-and-forget free antivirus.

Also, could you state which antivirus require yearly (free) registration (such as Avast) in order to continue to function? Because the "set-and-forget" is an important factor for me since I tend to install AV on several PCs.

Thank you for reminding me of MSE. I have now added it to the article as one of the AV's I looked into, but which have protection scores which are too low for me to recommend. The problem with MSE is that although it is very easy to use, the protection rating for MSE is lower than the vast majority of tested AV's. Thus, I would highly advise against using MSE. It used to be good, but has now fallen very far behind the rest in terms of true protection. Some tests even use it as the baseline against which all others are compared.

Thanks for the clarifying that, it's good to know.

What about my second question? It's really crucial for my choice process.

"Also, could you state which antivirus require yearly (free) registration (such as Avast) in order to continue to function? Because the "set-and-forget" is an important factor for me since I tend to install AV on several PCs."

I'm sorry, I just noticed this reply. As far as I know Avast is the only one in this list which requires registration. However, please note that I have not tried out all of these on my system, and thus cannot be entirely sure. If you find that any of the other programs in this article do require registration please let me know and I will include that information in the article. Thank you.

I too intensely dislike the newer Avast. I used to work really well, but starting this year (even though they said they still supported Windows XP) every attempted update crashes and will not complete. Secondly, it is constantly trying to change my search page to Bing or Yahoo will and not allow my current Google. I have read complaints from others who state that once having allowed the changes they cannot be undone. Point 3, the newest update has severely slowed my ability to use the internet and even do anything locally on my machine (once I uninstalled Avast, everything returned to usual).
I will no longer use Avast! Especially since the recommend Yahoo and not Google. I no longer use Yahoo because of spam issues.

"Bitdefender Antivirus Free Edition" has a serious problem, I tested it on three different computers running Windows 7 x64, and on each one the program/installer was in Romanian and the option to change the language was greyed out, this issue has been there ever since it came out and I never managed to find a solution for it.

Also, I'd like to know your thoughts on "ZoneAlarm® Free Antivirus + Firewall 2015" I've used it in the past and my experience with it was quite positive.

That's a strange problem to have with Bitdefender Antivirus Free Edition. If you don't mind me asking, where did you download the installer from? As for ZoneAlarm® Free Antivirus + Firewall, sadly it's not suitable for this article as it's more of an Internet Security Software than a straightforward antivirus program. This is a distinction we make with this article because all of these software must be able to run with a firewall of the users choice. For the article on the Best Free Internet Security Suite (which includes ZoneAlarm) please see here: Thank you.

I always download it from Bitdefender's official website:

Thanks for pointing that out, I will check the other article.

One more thing, I'm curious as to why "MSE" isn't included in that list? From my experience it's an excellent set-and-forget antivirus and correct me if I'm wrong but I believe it has been integrated in Windows 8 and higher.

That's strange. Is it possible that it is detecting the language of the systems you are installing it to? What is the set language of the OS you are installing to? Also, if anyone else has experienced this same issue with Bitdefender Free please respond and let me know. Thanks.

Not possible, all three computers I tested this issue on they are in English.

I also just tested right now on my own laptop (running Windows 8.1 x64) and I'm having the exact same issue.

Screenshot (before):

However I managed to find a workaround for this issue here:

Screenshot (after):

Thank you very much for the digging. I was unaware of this problem. However, I have now added a link to the post you discovered to the article. I'm sure this will help many others who otherwise would not have been able to use this quality software. Thanks again.

I tried it today briefly but it was disappointing. During the initial scan it stated that it found and cleaned 16 infected files which is highly unlikley considering the semi-empty PC I was testing it on, but even when I opened its log, it was empty. Also, the fact it has no options to speak of leaves a lot to be desired.

Indeed, I wanted to try it several times but was unable to due to that problem.
In any case, I'm glad I could help.