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.

Read more about Antivirus Engine and other related details at the end of this article.


Rated Products

Kaspersky Free Antivirus/ Kaspersky Security Cloud  

The paid security giant forays into free category and outsmarts its rivals

Our Rating: 
License: Free (Limited features)
  • Similar signatures & cloud features as its paid counterparts
  • Performance impact is decent on higher end systems
  • Strong behavioral blocker
  • Attractive GUI with no ads
  • Top-notch detection and always up-to-date
  • Thorough malware removal and disinfection process
  • Privacy policy (complies with GDPR)
  • Default settings cover most users
  • Bundles with Kaspersky VPN (can be uninstalled)
  • Fairly good web protection
  • Powerful exclusion settings (even for specific modules)
  • Extensive scan logs
  • Protection settings are locked with presets in Kaspersky Free Antivirus (KFA) [is available in Kaspersky Security Cloud]
  • Long but thorough system scans
  • Performance hit becomes worse on lower end systems
  • Slow update installation
Read full review...

Avast Free Antivirus  

The only antivirus with a fully customizable installer and selection of user preference components.

Our Rating: 
License: Free (Limited features)
  • 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  • Excellent malicious URL blocking, network protection, outdated software checking, integrated password manager, and comes with a rescue disk.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
  • 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
  • Offers Google Chrome and various bloated secondary components during install [Choose custom install]
Read full review...

Comodo Internet Security Premium  

Provides a multi-layered protection scheme with HIPS, sandbox, antivirus and firewall.

Our Rating: 
License: Free (Limited features)
  • 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
  • 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.
  • Chromodo browser, Yahoo search engine, custom DNS and Geek Buddy offered during default install. [Click customize installation during install]
Read full review...

Qihoo 360 Total Security  

This free antivirus is better than most commercial ones.

Our Rating: 
License: Free
  • 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
  • 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
Read full review...

Avira Free Antivirus  

A free antivirus with high quality signatures, very fast updates and less false positives.

Our Rating: 
License: Free (Private/Educational use)
  • 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
  • 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
Read full review...

Panda Free Antivirus  

Gives you antivirus protection with low memory and CPU usage, and collective intelligence cloud security.

Our Rating: 
License: Free (Private/Educational use)
  • 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
  • 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
  • Watch out for Panda security toolbar during install
Read full review...

Honorable Mention


Related Products and Links

How to make an antivirus engine

Other Articles By Chiron

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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.



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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Please rate this article: 

Your rating: None
Average: 4.3 (2219 votes)


It's important to note that idle RAM usage is not the only parameter to check if a software is light or not. How an antivirus affects application launches, installing/uninstalling softwares, boot time, archiving and extracting, file copying, downloading from web browsers, processor and ram usage when idle and during scans/updates along with various other factors determine the performance impact of an antivirus.

On a lighter note, Qihoo 360 usually took only around 30MB for me on idle without additional engines. What we can infer from this is that system configuration also plays an important role on the same. Additionally using any optimization software involves some knowledge about the same, but Qihoo's own tools are pretty safe to use and doesn't involve registry cleaning or advanced optimization techniques. But I wouldn't still recommend 360 TSE (Essentials) over 360 TS because it has slower updates and sometimes more false positives for some reason.

Thanks for the quick reply. Reading other glowing reviews and user experiences of 360 TS it does seem I'm in the minority regarding RAM usage. I was wondering if there was a conflict with Zemana AntiLogger Free as 360 TS also has an anti keylogger component but disabling ZAL made very little difference. I'll persevere with 360 TS though because fundamentally it seems pretty good.

I'm not sure how much I trust Qihoo and their products after reading how easily they got duped into whitelisting malware ( Not only that, but the article goes on to point out that "Testing bodies AV Comparatives, AV-TEST and Virus Bulletin decided to revoke all certifications and rankings awarded to Qihoo 360 products last year after they found that the products submitted for testing behaved differently from ones offered to customers."

Thanks for posting the article as well as bringing that to my attention. Qihoo should have double checked the products before whitelisting them. About the revoking of certifications, that's definitely between them and the testing bodies. But when Qihoo 360 TS already does splendidly well with the default configuration that I tested (rather than the modified version submitted to testing bodies) there's little for me to complain about here. But like MC has mentioned before, using software's in their default configuration is unacceptable unless you want to go through the "easy" route. Many users customize the product according to their tastes and hence the level of protection/usability/performance varies according to each configuration. Hence testing products in their default configuration is not exactly the right way to do. It just seems simpler.

How can one trust a company that has found to be cheating by three of the widely respected anti-virus testing companies - AV Test, AV-Comparatives and Virus Bulletin to the extent that all three testers have stripped Qihoo 360 Total Security of their test results.

You can make what you will of the reasons given for the test submissions (Chinese v external market) but ultimately the true detection performance is a matter of configuration.

"Investigations by the three labs found that all products submitted for testing by Qihoo had one of the product's four available engines, provided by Bitdefender, enabled by default, while a second, Qihoo's own QVM engine, was never enabled. This included versions posted to ostensibly public sections of the company’s websites.

By contrast, as far as can be determined, all versions made generally available to users in Qihoo's main market regions had the Bitdefender engine disabled and the QVM engine active. According to all test data this would provide a considerably lower level of protection and a higher likelihood of false positives. Options are provided in the product to adjust these settings, but as the majority of users leave settings unchanged, most tests insist on using the default product settings to best represent real‐world usage."

Maybe most users do leave their settings at default in which case the test results were certainly erroneous. On the other hand, using security apps at default settings quite often yields unsatisfactory results and this is not how Windows security should be configured. MC - Site Manager.

I ran 360 for about a year but got tired of the same annoying issues all the time. It'd get warning pop up about stuff that I'd already white-listed and despite continually saying "yes" over and over again I'd still get the pop-ups. Not to mention that the false positives are just excessive. They are all from the 360 engine, which is always on. It can't be disabled even if you have the other two engines enabled. If you could run it with just the Avast and Bitdefender engines it would be great.

I switched to something that only gets a nod in the honorable mentions here - Sophos. You essentially get their corporate product, complete with cloud-based management, for free for up to 10 computers.

I didn't have a problem with the same application after white-listing it. Since Qihoo has high proactive (behavioral/heuristic/hips) detection capabilities it might show false positives for certain files. Most of which I have seen is from various C++ and Java programs that I have written, and since there is code injection involved it detects as heuristic (possible) malware. But it still doesn't delete those files, but is left upon to user's choice to analyse and determine which files to keep/remove.

The notifications that you might have received and answered "Yes" to might be when an application was trying to access protected areas of the registry. Qihoo has registry protection feature where important areas of registry are being monitored. So those pop-up's you receive might be for individual registry entries related to a specific application. But when you click "Allow all" instead of "Allow" will give access for that software to all related registry areas instead of having to click Yes separately for individual entries. But this does not mean it "white-lists" the software during real-time/on-demand scan. You might have to manually do that by going to Virus scan->Trust List->add related .exe files.

Regarding Sophos, it's good but quite simple for my tastes. For a cloud antivirus it's not light, the install takes more than 900MB disk space (Program Data+Program Files folders) and also has high RAM usage (>200MB). Also the dashboard (controls) are present in a web-like interface accessed through a browser! As for the good parts if you have multiple systems to manage it's sweet. Also it's web protection is great, parental controls are charming with good PUP detection as well as no adware present in it.

360 Total Security should be changed to "Free for private use only". Its website at, under Category>Others, states "The software is not licensed for any commercial business activities, profit-based business activities, or revenue-generating business activities." (Their wording is a bit unclear though.)

I thought Panda was the top rated... I can't keep up.... I had 360 and than found out Panda was better and now Panda is last and 360 is first....DANG!

Dont take all the tests too serious.Panda IS a great antimalware,and its okay light too.It would be my number one choice if I wanted a free antivirus.
Your ass is covered with Panda.

"Better" is mostly a subjective word. Like I already said in the Introduction part there is no Best Free Antivirus so I went through the Pro n Con structured layout in this article to make it easier for you to find an antivirus that best suits your needs.

The best thing you can do is to stick with your current antivirus, most preferably one among these mentioned in the article, while also reading through other alternatives if any particular feature in an antivirus attracts you. Otherwise you can try all of them, and stick with one. This is the best part of any software that's been offered for free.

I endorse 360 Total Security. I was introduced to it when a local print company using it picked up a threat on my USB that MSE had not detected.
now use both it and MSE and find they work seamlessly together.
I also like the Optimise Option on 360

I installed qihoo from the link and ran a scan. Now it has DESTROYED most of my programs. None of my browsers will work, I can not access Sustem Restore or Task Manager and no way to download replacements. I am in despair. (This is coming from an IPad>. M HELP

Got my system back. Thank God and Gizmo for the Ulimate Boot disk. Now following instructions at [link removed as it contains links to red-rated scam software] Although the registry keys seem to be gone already. Perhaps it did not install properly in the first place.

Further baffling, now Comodo is actually running for the first time since I installed it.
[Moderators comment: Please be aware the link you posted is to a scam site that appears to be legitimate but contains links to the red-rated SpyHunter rogue software. I even detailed this a short time ago in a post below. These folks set up dozens of domains linking to this rogue software and keep changing them as each site goes red with WOT (Web Of Trust). MC - Site Manager]

Your "download" button for Comodo is actually the link to Avira.
Also, there's a separate page for Linux antivirus.
I'm not so sure there's really any point because Linux is so virus-resistant anyhow. But it's good to see Tux getting some love.

Thanks, the link has now been corrected.

@ George J.
New to-be-considered contender in this category: SecureAPlus ( combining 12 anti-virus engines

SecureAPlus is considered to be a companion AV (an AV used for second opinion apart from your primary antivirus). It's mainly an application whitelisting (trusted) software that uses a block-first approach, where system is locked down after it's install and anything that's newly installed is considered untrusted/blocked unless you allow it or is available in their continuously updated list of trusted applications.

It also has AV scanning modules with it's engines available across the cloud that will block anything that has been detected as malicious. But from the FAQ ( it appears to be free only for a year, and then it can be extended only by adding referrals.

Dear editor, the "Go straight to the Quick Selection Guide" link on the page does not seem to work, please fix it.....

This has now been fixed. Thanks jawad.shafiq for the comment.

Many people would never consider Qihoo for fear of a Chinese government-mandated backdoor. True, this is speculation, but it does seem worth mentioning.

What made me nervous, was they do not appear to have a paid version.
When a company that has paid versions, also gives a simplified free version, I can sleep at night.


Qihoo 360 is multi-billion dollar company (unlike most other companies in this review), has more than 4200 employees and the revenue it might generate from selling it's antivirus product is quite meager. Just like Google, most of it's revenue comes from advertising (~68%), internet value added services (~30%) and only less than 1% from selling third party software. What started as a paid antivirus switched to the freeware model to gain market share and popularity in China.

I've used Qihoo in the last year but when i saw the same program was getting installed on other people's computers by malware and there are multiple sites telling you how to get rid of it because the uninstall doesn't remove everything I switched. True to form it did not want to uninstall and many parts had to be manually removed after the uninstall claimed to be successful. Multiple reboots later it still had processes running.

From the comments what I can understand is that certain people have been tricked into installing a rogue software that masked itself as 360 Total Security. There could also be programs that promote 360 TS and bundle their product with the antivirus software which may or may not be fake. Same is the case with many programs endorsing Google Chrome.

Now the end user is responsible in both these cases if 360 TS (fake/not) appears on their system in this fashion. The solution to this is to download programs from their official website unless specifically stated at Gizmo's Freeware with links to alternate sites.

Until last February I used to have 360 TS (before switching to Windows Defender) downloaded and updated on one of my systems through every iteration from version 5 and I have not experienced any problems like you've mentioned. To confirm that I downloaded 360 TS again day before yesterday, and had the same experience. It had the fastest install/uninstall times among it's counterparts, completely uninstalled itself without any "parts/modules" left behind, had no so called "processes" related to 360 TS running in the foreground/background after un-installation and reboot.

About the files left behind, after un-installing an antivirus you are supposed to reboot your system before the files are removed completely, which is why you might have seen folders of files related to it left behind. Even after reboot there might be certain empty folders left behind and some with files of few Kb's which does not affect system performance. This is true for any antivirus out there.

In the case of 360 TS the folders left behind after reboot were:-

  • 360 - C:\Program Files (x86)
  • 360 Quarant - C:\ProgramData
  • 360safe - C:\Windows\SysWOW64\config\systemprofile\AppData\Roaming\360safe 
  • 360Disabled - C:\Windows\Tasks

The same is the case with Avast::-

  • Avast Software - C:\ProgramData\AVAST Software
  • avast Antivirus! - C:\Program Files\Common Files\AV
  • Avast - C:\ProgramData\AVAST Software\Persistent Data
  • Avast Software - C:\Windows\System32\Tasks

This can be replicated for others too.

You had mentioned that 360TS had been installed by "malware" [from the very little information provided by you] which caused the after-effects so the original program is not the one at fault. The software from the official site doesn't include any adware/malware like you say, and this has been confirmed prior to writing this review. If you have any doubts about the same, and willing to trust Gizmo's Freeware for our reviews, you should try it yourself based on the recommendation before following up to what others have to say.

I installed qihoo from your link. It DESTROYED most of my programs, including Firefox and most of my start-ups. I could not uninstall it (went into Safe Mode to delete manually, but who knows what else is there)", and can not access Task Manager or System Restore. I can not install any replacements fort he destroyed programs,keep getting "no such interface" errors.
I am running System Restore from the Ultimate Boot CD and praying.

Over the years I've seen this issue caused by a variety of (mostly) security software especially in systems where several different security software apps have been previously installed. The fix involves the correction of registry errors. I suggest you Google for whichever you believe to be the most satisfactory solution but personally I do not recommend the use of automated registry tools, so the assistance of a qualified tech might be more appropriate. MC - Site Manager.

I too have had no issues whatsoever either with the running of this antivirus (when obtained from the official source), or its removal. This thread provides some insight into what might have happened to others. MC - Site Manager.

I definitely had obtained it from the official source. the uninstall appeared successful but left running processes behind. Your experience may vary.
My experience and the fact that it is installed by other malware for some people is enough for me to never go back.