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

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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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Average: 4.3 (2084 votes)


Real World Protection Tests at AV-Comparitives... Panda scores 100% at the expense of too many false positives (34). Good results for Qihoo, AVG(IS) and Avira(Pro).
Take a look at Tiranium Internet Security. A splendid antivirus with firewall. Seems to be getting rave reviews.. Certain community video review tests Review 1 Comparitive review 2 Review 3 If you aren't interested there's also a Cloud Scanner that you can work with your current antivirus and a KeyLogger provided by the developers
As MidnightCowboy said, at this time it is not a good fit for this article. However, I will keep an eye on it and see if it continues to improve, including testing by independent testing agencies. Thanks.
An emotional Paste from DubSeven the developer, and the reactions Tiranium will be closed in a month.
One great comment. "I saw how everything depends on money. The computer security is no longer about security but about money". You could pretty much extend the first part to everything on the planet. MC - Site Manager.
I guess you meant 'planet'. I'm surprised that the developer is an 18 year old kid, and was 13 when he first coded Tiranium. Those insults must have hit hard on him. But he did some great work at such a young age.
Indeed. The trolls enjoy their work however and must be really pleased with the result. Some might even suggest that one or more of the established names in the industry might have been involved. It's well known that some vendors employ legions of fanboys and trolls to post good and bad "reviews" online about competing products. Thanks for spotting my typo above which is now corrected. :) MC - Site Manager.
Tiranium is an interesting project but is just a one man show with a small team of "helpers". We won't be featuring this here (or anything else like it) unless it develops a lot further and begins participating in recognized independent tests. MC - Site Manager.

Well, I tried it, I'm sure it's a wonderful program, BUT, even after a careful installation, it nags the devil out of you to sign up for the stuff you didn't want. Have been using Bitdefender for a year, no problems. Before that, was using Avast, my favorite, but Avast changed something in their detection rules and it would not allow me the see my security cameras for remote sites. I have income properties in other states.
So, ran a scan with the Comodo antivirus, O (zero) detection. This tells me that the Bitdefender is doing its job, and I am ALL OVER the internet.
Sorry, I can't for the life of me see why anyone would rate this as their number 1 source for protection. It's intrusive, and it nags the heck out of to sign up for the add ons you didn't want in the first place.

Were these messages you saw in the lower-right corner of the screen in a small popup window? If so, then I just added advice on how to disable these advertisements to the article. I apologize, I had meant to mention this previously, but forgot to include it in a previous revision.

Excellent review as usual Chiron. I'd been using the free Avast AV/Comodo firewall combo for about 2 years but problems with Avast updating and your favourable Comodo AV review led me to ditch Avast and replace it with the full Comodo Internet Security free suite. Much less hassle having everything in one place and not having to worry about conflicts and creating exclusions etc. Things are now noticeably quicker.

I'm happy to hear that. It's very nice that users have the choice of whether to use Comodo Firewall with Avast Free. They are a very nice combination. However, I personally also use Comodo Internet Security, and prefer it to any other combination. That said, each computer, and computer user, is different. Thus, the more top-quality options which can be presented the better. Thank you very much for letting us know that Comodo Internet Security worked very well for you. If you run into any problems, or have any questions/suggestions, please do let us know. Thanks again.

One thing I didn't mention was what a nightmare it was to uninstall Comodo firewall to do a clean install of CIS Premium, even using your guide on the Comodo forums (Revo, both removal tools etc). Lost internet connection, CIS wouldn't install and restore wouldn't work due probably to either remnants of Avast or Comodo firewall. I finally got everything to work a considerable time later.

Did you make sure that the firewall driver was correctly removed before rebooting into Safe Mode? Sadly sometimes that is not removed by the uninstaller, and I don't believe the removal tools correctly remove that either. Either way, it is true that Comodo Firewall doesn't always uninstall easily. However, the methods I suggested, which you followed, will allow it to nearly always uninstall correctly. It seems that you ran into some bad luck. By the way, how did you eventually get it to work? Thanks.

You're right about the firewall driver. Neither removal tool nor the uninstaller removed it. Your advice to remove it manually is several steps after rebooting into safe mode, so it hadn't been removed before doing this.

Regarding how I managed to get things to work, things are a little hazy due to a fair bit of red mist, but I went through the uninstall procedure again with Avast (2 removal tools like Comodo) and Comodo Firewall, still wasn't able to install CIS but at least restore then worked so as a last resort I restored to before trying to uninstall Comodo Firewall, and just went through the whole laborious process again and eventually it worked.

I think perhaps I should move the advice about manually removing the firewall driver into the main advice section of my topic. Then again, it's not something which most users would like to do. I'll have to think about it some more, but your experience has given me a lot to think about. Thank you.

Good Day A ! Hi George.J ! I am a current user of 360 IS and am considering switching to 360 TS for support reasons as you know. I'm curious if you could tell me more about your experience with 360 TS compared to 360 IS regarding detection rate, resource usage, boot up time, scan time, and how well 360 TS plays with other software, such as MBM and SAS. Never mind George, I have already found answers to my questions.

Well am back to using 360IS again. The reason is 360TS requires more resources on my system. The TS version uses around 150MB RAM while the IS version is very lightweight, using only around 30MB. Additionally 360TS adds other features like SpeedUp, Junk CleanUp etc, which aren't actually required for me, although it might be useful for others. While 360IS is clean as a whistle, guess it's the best antivirus I've ever used. Sadly the product isn't updated frequently like 360TS version. :( For a comparison betweeen 360 IS and TS in detection check this video review. If you want to watch various community video reviews, you've got 360TS MazaiTest 360IS Review 360TS viktik 360TS without BD and Avira engines 360TS yigido Overall excellent results from all sides :)
I agree with your findings although with an i5 and 8G in my dual booted desktop I'm not too bothered about resource use for anything. Unfortunately, 360IS is being discontinued in favor of 360TS so I'd rather use something that is being fully supported. MC - Site Manager.
360IS isn't discontinued. It just had an update today :D It's just that they are concentrating more on the TS version.
Not yet it's not, but their plan is for TS to replace 360IS, although they haven't said when. MC - Site Manager.
Honestly performance matters to me. Here's my findings 360TS is much heavier on the system than IS version. Idle Memory Usage 360TS - >150MB RAM 360IS - <40MB RAM Scanning Memory Usage 360TS - 320MB RAM , high CPU usage touching upto 95% at times, Disk Usage is also very high 360IS - <60MB RAM, low CPU usage less than 25%, Disk Usage very low. You can see the difference. :D It doesn't matter if 360IS doesn't get product updates, I think I'll continue to use it. Maybe I'll stick with TS version on my gaming system. Still it's too heavy.

Please consider Qihoo 360 internet security:

Very well reviews product in

Thanks for doing this.


Am back to using Qihoo 360 IS, and it's been excellent. Excellent independent lab test results, very light on resources and clean installer (which is not the case with most free antiviruses). The Total security version is too much for me, as it also includes Avira engine excluding the BitDefender engine, which is not needed for me. But overall, a perfect suite. Moreover, it's good to see that Avira is offering a clean installer, which was not the case in the past. And also it's lab results are among the best. Had to switch from Panda as it was slowing down my system to a crawl :(
Update: It seems that the company has switched from 360 Internet Security (IS) and is favoring the Total Security (TS) version, as the last IS version dates back to January. So far 360 Total Security has been amazing for me. Works great as an antivirus and as a total security suite. Great performance, high detection, better zero day expolits (registry, files & system protection), keylogger detections, support and frequent updates, makes it awesome. By the way am using only the BitDefender engine, but even with Avira engine enabled it still seems very light. But I don't wanna go around and update Avira engine, so not using it.
Qihoo is not a bad choice at all. I'm also happy to hear it's light on your system. From what I have heard Panda is generally light as well. However, the heaviness of an AV is always, to an extent, system specific. Thus, you may find that when you get a new computer it is Panda that is lighter and Qihoo which is heavier. Thank you.
Honestly I expected Panda to be lightweight considering it being cloud antivirus. But the results just mirrored the lab tests at AV-Test with Panda rated lowest in performance, and lower than other Free antiviruses at AV-Comparatives for performance. But like you said, it also depends from system to system.
I will be considering them for my next major revision. Thanks.