Best Free Antivirus Software


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To begin with let me say this: there is no best antivirus out there. Why do I say this? Any product that you take will behave differently against various virus samples since the AV engines and other components incorporated in them are of different technologies.

While one product might have higher detection ratio, another might have better malicious URL blocking or virtualization techniques, yet another might have lesser impact on system performance and so on.

Antivirus Engine:

It is used for Real Time malware protection of files and is the core component to scan data on your PC for detecting and removing malware from hard disk, memory, boot sectors, network drives, removable disks, or from external network traffic (internet).

  • How does an antivirus detect malware:

Firstly you got the signature-based detection which contains an offline database of known patterns of malware downloaded from the internet which can identify specific malware codes or family of malware. Then you have heuristic based detection that identifies pieces of code that are unlikely to be found in legitimate programs and hence is prone to false positives depending on the sensitivity of heuristics. Virtualization and sandboxing unpacks or executes unknown programs in an isolated secure environment so that their behaviour can be analysed and scanned using the antivirus engine. The latest one is cloud based detection that requires a reliable internet connection and sends the suspicious scanned file over the internet and the analysis is done by the vendors' machine running the cloud engine.

  • Scanning for viruses:

Most antiviruses include these basic scan types: On-demand scan/manual scan is initiated by the user from right click context menu or from within the software. On-access scan is initiated when the resource is being accessed like running an executable, copying files from external drives etc. Scheduled scan periodically ensures that the system is free from malware by setting the time and frequency for scanning. Startup scan/quick scan checks most important locations like running processes, startup items, system memory and services, boot sectors and so on.

To be Continued in the next update....... Firewall, Proactive protection, Web protection components and more.

Honorable Mention:


Discussion And Comparison

1. Qihoo 360 Total Security

The Good:

  • Totally free, light on resources, extremely fast scan times and pre-configuration protection modes
  • Smooth running installer with no adware, pleasing UI and comes with many themes
  • Fast updates/fixes and excellent customer service with immediate replies
  • Great signatures with multiple engines and in-house cloud protection
  • Web protection addon, browsing locking, webcam, sandbox and usb protection modules
  • Online shopping protection, malicious URL protection and network threat blocking
  • Includes Glasswire Firewall and Windows patch-up components 
  • Great detection rates, with very high zero day protection
The Bad:
  • Speedup and clean-up tools might not be for everyone (not present in Essentials version)
  • Bitdefender or Avira engines not enabled by default 
  • Might encounter few false positives
  • PUP [Potentially Unwanted Programs] detection needs to improve
The Ugly: 
  • Nothing for the moment
The Truth: Rating 10 of 10 5/5 stars
 Home |  Download |  v8.2 |  bit version |  Fully freeware |  41.6MB |  Win XP-10, Mac OSX

2. Avast Free Antivirus

The Good:

  • Extremely light on the system with a modern and clean UI
  • The only antivirus with a fully customizable installer, selection of user preference components
  • Works best in hardened or lock-down mode, which blocks all unknown programs (medium-expert users only)
  • Top notch detection capability, many secondary components to offer variety to a wholesome software
  • Excellent malicious URL blocking, network protection, outdated software checking, integrated password manager, and comes with a rescue disk.
  • Deep screen technology that includes Sandbox and Safe machine components for protection
The Bad:
  • Bloated default setup, some ads and pop'ups
  • Account creation for further protection after a month
  • Lack of an anti-ransomware module, and Deepscreen disabled by default
  • Cloud reputation, Malware signatures and HIPS module needs improvement
The Ugly:
  • Offers Google Chrome and various bloated secondary components during install [Choose custom install]
The Truth: Rating 9 of 10 4.5/5 stars
 Home |  Download |  v11.1 |  bit version |  Feature limited freeware |  193 MB |  Win XP-10, Mac OSX

3. Comodo Internet Security Premium

The Good: 

  • Feature-rich with lots of options for customization along with setting tolerance against prompts
  • Tweaked settings gives the best 0-day protection among the pack
  • Multi-layered protection scheme with HIPS, Sandbox, Antivirus and Firewall
  • Industry grade firewall with options for learning and behavioural blocker
  • Low on resources with various graphical skins available and a clean user interface
The Bad: 
  • Painful for beginners to use it, not very newbie friendly 
  • Av-module is a bit weak especially the signature based detection
  • Auto-sandboxing happens for various legitimate files, troubles with FPS games
  • Too many tweaks needed for better protection
  • Buggy software and updates are released slow.
The Ugly: 
  • Chromodo browser, Yahoo search engine, custom DNS and Geek Buddy offered during default install. [Click customize installation during install]
The Truth: Rating 9 of 10 4.5/5 stars
 Home |  Download |  v8.2 |  bit version |  Unrestricted freeware |  208 MB |  Win XP-10, Linux, Mac OSX

4. AVIRA Free Antivirus

The Good:

  • Pretty light on the system and runs smooth without system slow-downs
  • Clean ad-free GUI, Ad-free installer, No pop-ups or ads
  • High quality signatures, very fast updates, excellent detection on non-zero day threats
  • Deep file scans with very less false positives
  • Avira Protection Cloud makes for an excellent cloud engine
  • Browser safety Add-ons available for major browsers
The Bad: 
  • Zero day protection (heuristic & behavioural shield) is very weak. 
  • Ineffective Browser launcher which is a memory hog (can be uninstalled)
  • Painful removal for detected files. Repeated scans from Luke Filewalker increases CPU & RAM usage. 
  • Multiple file exceptions needs to be added (real-time and on-demand)
  • No firewall/sandboxing/web shield technologies
The Ugly: 
  • Nothing for the moment
The Truth: Rating 8 of 10 4/5 stars
 Home |  Download |  v15.0 |  bit version |  Free for private use |  200 MB |  Win XP-10, Mac OSX

5. Panda Free Antivirus

The Good:

  • Low memory & CPU usage thanks to cloud protection 
  • Tiled UI with customizable interface and nicely rendered Settings interface
  • Collective intelligence cloud security - Downloading virus definitions is history
  • Good detection rates and behavioural analysis program
  • Fairly good web protection and hardware resource handling

The Bad: 

  • Dependant on internet connection leading to weaker offline protection
  • Slow scanning speed, no fingerprinting (successive re-testing same files) and at times issues with virus removal
  • Not really light, performance impact in web browsing, installation and copying
  • Certain false positives despite the information available at cloud

The Ugly: 

  • Watch out for Panda security toolbar during install
The Truth: Rating 8 of 10 4/5 stars
 Home |  Download |  v16.1.1 |  bit version |  Free for private use |  61.4 MB |  Win XP

Most Improved products of 2016:


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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.
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.